David Lynch Baritone
Instruments- discuss specific features, luthiers, instrument problems & questions
Todd, I see you've found the For Sale Forum here. That is a great place to find used instruments, although the usual caveats apply.
The reason I mentioned McSpadden in my earlier post is that McSpadden dulcimers are all good quality and eminently playable. They are also quite popular, so if you decide to sell one later on, you won't take a big financial hit. I see you've found a Folkcraft for sale here. Folkcraft are also of high quality. If you find one at a decent price, they are usually a safe bet.
You might check Craig's list for used dulcimers, but as with Ebay, the majority of instruments you find there are of questionable quality. Reverb is another online marketplace, but the prices there seem higher. And honestly, I would suggest staying away from online retailers unless you know the maker well.
As to your question about how to get your hands on a dulcimer to try them out, I can't tell you where to go in SLO itself, but I know some people in Los Osos who have a regular dulcimer gathering. If you wish, I could put you in touch with them. In the LA area there are lots of players and there are a few up in the Santa Cruz area and in the East Bay. In the summer months there are in-person gatherings you could attend when you could just ask to try out people's instruments, but not much is happening like that this time of year.