Buying a used bike off Craigslist can be very hit or miss. There have been a number of times that I attempted to buy something off Craigslist, had what seemed like an endless exchange of email and then had the deal just fall through for no reason. If you aren't going to have multiple days to get this done I wouldn't recommend Craigslist.
There is what might be a much better way. But I am conflicted because I believe that I am not supposed to post anything in these forums that advertises a retail store. So, with that in mind:
There is a very large retailer that operates in the USA. This retailer sells bicycles, and they have both a website and a store in Reno. You can purchase a bike off the website and have it shipped to the store, where it will be waiting for you to pick up. This store is also a convenient place to pick up many of the things you will need.
The bike you want to buy is a Huffy Cranbrook 26 inch. This is the bike that Burning Man uses in their "Yellow Bike" community bike program. They are the ONLY bike that Burning Man will accept as a donation if you wish to discard it after the event. They are also a fairly inexpensive bike, $99 from the website. Look at this web page for details:
http://blog.burningman.com/2013/08/play ... low-bikes/
Rod