I recommend Gardiner as well. The only thing close to West Yellowstone is the Madison inside the park. (Firehole is normally to warm by July)
Doesn't the Madison also flow outside the park?
John
p.s. And here all this time I've been living closer to Gardiner, you'd think I would have learned a long ago that I was wasting my time going fishing around West Yellowstone. (please note that I'm smiling.)
If you guys are there between the 14th and 21st, be sure to swing by the Campfire Lodge to say hello. We are having the Montana Fish-in during those dates. You're welcome to come and fish with us for a few if you'd like.