I will be studying in the US for the next couple of months. I am currently seriously looking into buying an low-end MTB. I am planning to use it to explore the neighbourhood, as well as to cycle up into the mountains near the city. The only problem is that most likely I won't be able to take the bike back to Europe with me. That leaves me with used <100$ bikes or a new $80 bike from Walmart. Today I actually walked to Walmart to see their bikes (the walk took 2.5 hrs in 40C/98F weather), and the problem is that I don't like them. Cranks seemed some kind of integrated (barely serviceable?) model, and brakes were cheesy even on a brand new bike. At the same time, I will only need the bike for next 4 months, and I am not a heavy rider.
What would you suggest? I tried exploring the local craigslist, but there are very few options in El Paso area. Are there any other good sources of used bikes in US? Police auctions or something similar? I also found one LBS located nearby, but they only sell new bikes from ~400$ and up. Not to blame them or anything, but it is a little to much for a disposable bike.