OK…
After the GF will be a perfect time to be visiting the north. I'm assuming this will be mid-late October.
2 weeks in the north only will be a good trip.
If you based yourself in Hanoi and took 2-3 day trips to other locations I would try to include the following:
HA LONG BAY/CAT BA ISLAND - To get here you are looking at a 3hr bus ride from Hanoi...hotel pickup...with a stop half way for a little village visit. The reason that they will do this is because the country really does look after its own. I've done this trip 3 times and we stopped at a different location each time. You'll find that you'll be inundated by vendors at this stop selling everything you can think of. I've been told that whatever money is raised from the tour busses here is split among the community so I usually buy some small trinket or a book or something....they're cheap as and these people are dirt poor. Just be careful not to flash to much green around as you will be surely mobbed lol.
Now instead of doing the Ha Long Bay trip from the designated area which is close to the Cat Ba end of the national park take the tip and book your junket just to the north at Bai Tu Long. The reason I suggest this is because the traditional Ha Long Bay tour is VERY touristy. This is the one that everyone talks about but I really think its a pain in the backside. There is so many people here that you feel like cattle being herded here there and everywhere. Not real relaxing!
If you take the Bai Tu Long trip you'll experience everything that Ha Long offers without queing up for hours and being dogged by vendors in boats constantly. Also Cat Ba isnt really all that great, try Van Don or Quan Lan instead.
Don't get me wrong though, this trip is definetly worth the effort and when you are drifting through the passages at night time surrounded by thousands of limestone rocks jutting out of the green waters you will be relaxed. These junkets all have a plentiful supply of good fresh food, alcohol and company. If your lucky you can even take a dip in the warm waters at night surrounded by the glow of bioluminescense....magical.
HANOI - Is the capital and is a very different city to Saigon. Its still fairly full on with the traffic but is at the same time a lot more laid back. The nightlife is fairly quiet but there are still a lot of cool things to see and do there. Its an easy city to navigate and I would suggest hiring scooters to get around. If your not comfortable taking on the masses of traffic then hire cyclos and tour the city that way. The old quarter is vietnam and is definetly worth a visit...I'd suggest staying there. It's vibrant, smelly, noisy...its awesome lol. Hao Binh Palace or Hanoi Hilton are 4 star places with wireless internet and comfy rooms. Brekkies are always included in hotel prices.
Be aware of the traffic here..there are around 2 million bikes in Hanoi alone and the traffic is constantly flowing. The good thing about it is that it is constantly moving and if you hold your line when crossing the roads it'll simply divert and flow around you - no sudden movements lol.
Things to see and do include, more just experiencing and getting out on the streets here. The Old Quarter is very interesting to wander through, as is the lake and park. The Ho Chi Minh Maeusoleum is also worth a look...the man himself is still on display! They also have this cool waterpuppet shows in the old quarter that are worth a look. Plenty of great eateries are to be found as well. Take your lonely planet guide and you'll find them.
DANANG - You can catch a fairly inexpensive flight down to Danang and from there you can visit some great places. It has a spectacular beach with real surf and the seafood restaurants are superb.Plent of good bars, cafes, restaurants and even nightclubs in Danang, just ask around and you'll find them. You can hire bikes and ride yourself, or as a pillian and explore the coast line with Monkey Mountain, Son Tra Peninsular, Lon Co Beach etc...you can also visit China Beach and Marble Mountain to say you've been there.
HOI AN - About 40 minutes from Danang, this joint is great. It has the best tailors in Vietnam. They can custom make anything you want for bugger all money. This is where most travellers get their suits, dress shirts, dresses, shoes made. But apart from that it also has heaps of temples and pagodas to wander through. It is a very old town and you can see remnants from the Cham dynasty everywhere. You will enjoy this place. p.s. visit cham island while your there!
HUE - You can get there from Danang by bus, or car, or bike and the trip there across the Hai Van Pass is awesome! Better than the Great Ocean Road and tighter than Brown Mountain....it was featured in an episode of Top Gear and it is fun. Once your in Hue get ready to be a tourist. There are so many tombs of ancient emperors, pagodas, an emperial city, national parks to trekk in, visit fishing villages whilst travelling the Perfume River, palaces...the list goes on. But just as impresive is the cuisine here. I think Hue has the best eateries in the country.
MY SON - UNESCO world heritage site that was built by the Champa kingdom 1800 years back. You can get there by a 1hr bus trip or by bike from Hoi An. Plenty to see here..sort of like Angkor Wat in Cambodia. Night trips are done as well.
SAPA - These are the mountain regions north of Hanoi and are incredible. Again when I have been I hired dirt bikes but you can easily organise a 2 or 3 day trip through anywhere in Hanoi. These people are the ethnic minorities and are the purest form of Vietnamese lifestyle. Very well worth the trip to discover beautiful scenery and a basic way of living that can make you feel a little envious when compared to our hectic lives. Brilliant trekking is available.
Well there you go, that should get you through a couple of weeks no probs....It'll be enough to give you a good taste and I gaurantee you'll be back to visit the rest.
A couple of things to remember...when visiting temples, palaces etc...dont wear singlets/low cut tops or skirts...they find this offensive. Dont flash your money around as your always being watched and if they see a roll of notes you'll be quickly surrounded by sellers and this can be very annoying. With the exception of food don't buy anything without first haggling. Everything is negotionable - dont be ripped off...trust me they'll try lol. When you do haggle, do it with a smile...if they lose face publically they can get very nasty. I've seen tourists being abusive to the locals once drunk and being set upon by dozens of locals wanting revenge. Basically dont be American lol. Always drink bottled, unopened water, even brush your teeth with it. As your not travelling with men I wont warn you about the millions of hookers you'll come across....that can also be a little intimidating. Get amongst the traffic, either by bike, cyclo or tuk tuk. Part of experiencing the country is smelling and hearing the place. You will slightly rob yourself of this in a taxi.
Apart from that they are a beautiful, friendly race who are always quick with a smile and a chat. Your gonna have a ball!