Hey Josi, looks like you're new to CS--welcome! April 20th is a pretty fun time to be in Boulder, and the weather's usually great. The best way to find a couch to surf is to send personal Couch Requests to folks who live in the city you'd like to stay in. Doing it a month ahead of time is more than enough notice for most people, usually 1 to 2 weeks' notice is just fine. In the mean time, a good way to get a reference or two on your CS profile is to attend your area's mixer. The last time I went to one in DC I had a ton of fun. Having references shows a host that you are a trustworthy surfer and are interested in a CS experience. Hope this helps, and maybe I'll see you in Boulder.