The problem with Boise and many towns in MT/WY/ID is that cab service is really crappy. BIL cab wait times on "spot" calls is over an hour on good weather days. I can't speak from experience in BOI but I would expect similar circumstances. Call a cab pick up ahead of time to eliminate this.

For parks, there is the big city park along the Snake River which is a big hangout for joggers/bikers ect. It is quite long, my memory is 0.5 mi. There is even a kayak section in the river. Downtown used to be pretty yuppified but I heard that some of it went slightly down hill after the tech bust but with Micron and HP's fortunes back up, I'm sure that it is in good spirit again. I know of a couple of SBUX downtown and they usually have wifi.
http://www.starbucks.com/retail/locator/default.aspx