Great question. I would be cautious about sharing ideas right away with the group. I'll tell you my story which has to do with screenwriting, but it could apply to travel writing as well.
I shared my teleplay idea with my screenwriting group; it's been completed for a couple of weeks now. Lo and behold, a guy in my writing group wrote a teleplay that is very, and I mean very similar to my teleplay. You could take my teleplay and put it into his. All you would have to do is change the names, setting, etc... Needless to say, I'm speaking with a copyright lawyer because I'm serious about writing, and I want to protect myself. I want to know every nuance of copyright laws, especially when it comes to verbalizing your ideas or completed projects. It was a tough lesson for me to learn, but I leaned it. I will not share my ideas with any writing group again.
The writing groups I would look for are ones that offer writing exercises. Perhaps they analyze work that is already written. You could take a travel writing article and re-write it or discuss the structure of it. Any ideas you have, keep them to yourself or discuss them with the organizer if you trust him or her. Good luck!