HI Fisherman's Wharf is probably the best budget lodging in San Francisco. In a city where it's difficult to find a hotel room for under $100, this hostel is a great option for students, couples, road trippers, and even organized groups (call for special rates). Private rooms are a good option for small families.
Aside from the price, which is matched by the other two Hostelling International hostels in San Francisco, the best part about this particular hostel is its beautiful location. It can be found in the Northernmost part of Fort Mason, a federal park area and former army station for Spanish and later US troops. The hostel itself is a historical building with small displays and a mural dipicting its previous functions. The hostel is also within a short walk of the tourist district of Fisherman's Wharf, and the trendy and beautiful Marina District. There are also a number of nearby buslines that will take you to Chinatown, downtown/Union Square, the Mission district, or the Golden Gate Bridge.
Some tips for staying at this hostel:
-Make reservations early for the high volume season (approx. April-October).
-Consider staying in a private room if you are travelling with 1-3 other people. The price will often be lower per person than staying in dorm beds.
-Take advantage of the free breakfast in Café Franco while enjoying a beautiful view of the Bay.
-The staff is among the friendliest and most knowledgable you can encounter, so don't hestitate to ask them questions!