Best Airlines to Fly to the U.S. and Back

I'm hoping to get some ideas from people who travel frequently as to which airlines are the most economical to fly to the U.S. and back from Guadalajara. I'm not sure whether using a Mexican airlines would be better than one of the U.S. airlines. I sure would appreciate any advice or ideas. Travelling to Denver over Christmas and New Years. Thanks in advance. All replies would be appreciated.

At Xmas it will be expensive with just about all of them. Check with Volaris.

I just booked my Mother round trip for Thanksgiving 11/18-12/2 PDX-PHO for $272.00

I just booked my son to come here from Vancouver at Xmas (Dec. 20). I checked with every airline. I ended up going with Alaska. It was almost double the normal fare. It cost me $980USD + 30,000 air miles. Normally it is about $600 all in. Some of them (US Air, United, Delta) wanted almost quadriple ($2500 USD) for this time period.