Reddit mentions of Designing the Conversation: Techniques for Successful Facilitation (Voices That Matter)

Oh hey, I just did something super similar at my first job.

One of the most valuable things I found was Steve Krug's usability testing script. I really wanted to get the best feedback I could, and this went a long way to help me coach the folks I was talking to. He also wrote two real good books about UX, with "Rocket Surgery Made Easy" focused on testing

Another great resource was Ross Unger's talks, book, and articles on Guerrilla User Testing.

Basically, I go through the script, and get the people (never call them "users" directly) talking out loud while they accomplish tasks. If you can get a second person to take EXTREMELY good notes or record it, that'd be even better.

As for the Starbucks vs. visiting the trails, it depends on your target market. Do you want folks already using the trails to get more out of them and have a better experience? Or do you want to get more people from the community using these resources? I know most people would want the latter, but if you focus on the former you can start to iterate a better experience for everyone and then have a broad push for larger audiences.

Anyway, I digress. But usability testing doesn't have to be expensive or super formal to get a lot of it.