Well, I might as well jump in, too. I use Verizon and have always had excellent service at Old Faithful, Canyon, Mammoth. Sometimes (not always) I have service at Norris, and one time I actually received a call while driving through Firehole Canyon (near the exit to Firehole Canyon Drive). Scott Bryan In a message dated 5/4/2010 8:10:57 P.M. US Mountain Standard Time, riozafiro at gmail.com writes: I have Tracfone, it works in the Old Faithful area, around 7-Mile Bridge and in West Yellowstone to about 14 miles west, just past Hebgen Lake. Then I do not get service again until I am almost to I-90 outside of Butte. Haven't tried it in Mammoth. It is a pay-as-you-go service so you can buy just what you think you will need for the trip, but it does not give me reception throughout the Park. -------------- next part -------------- An HTML attachment was scrubbed... URL: </geyser-list/attachments/20100505/2243d30d/attachment.html>