<map lat='10.771928557041234' lng='106.68617248535156' zoom='11' view='0' float='right'/> Saigon, currently better known as Ho Chi Minh City, is the largest city in Vietnam.
In Saigon you won't have the feeling of being out of the city for a very long time... But don't panic!
Saigon is covered by an extensive bus network, which reaches well into the suburbs. You can get the map on paper for free at Ben Thanh market.
There are 2 main roads: AH1, super busy road along the coast, crowded and in good shape. Ho Chi Minh highway, going through the highlands, more scenic, some parts have very light traffic or bad roads.
Bus 43 goes to the beginning of this highway. Get off at Nguyễn Thị Định. Bus 15 follows approximately this route and bus 22 this route. Probably the best bus to take is 19 which starts at Phạm Ngũ Lão and goes out to the New Eastern Bus Station (the furthest point on AH1 that any local bus goes) along this route, which is perfect for hitchhiking.
AH1 is QL1A on some maps. To go to the north, like Nha Trang, Da Nang or Ha Noi, you could try going to the junction of QL1A and DT43. It's a highway, where lots of cars, buses and some tracks are passing by. And this place is easily reached by bus from the city centre, check out google maps directions for public transport.
Take a bus to Bến Xe An Sương. This is a huge bus station, so there are about 15 lines from somewhere in the centre going there. Walk out of the bus station and you'll be standing right on the motorway that leads straight to the border.