i ride solo in the area between harlingen, los fresnos, and rio hondo. i know of a few groups in the area, but i've never hoked up with any of them. all of the organized events in the valley end up
here. for mountain biking i just head outside of the valley. there's a spot in brownsville that's take it or leave it and parts of the trails in mission may still be open.
here's a few of the groups i can think of
http://www.facebook.com/pages/TEAM-MCALLEN-CYCLING/119119181442286
http://www.facebook.com/pages/Wallys-Bicycles/110204165687954
http://www.texsunrandonneurs.com/Home.html
http://www.riverrockets.com/
http://bicycleworldrgv.com/articles/rides-and-events-pg37.htm
[This message has been edited by Walter Kovacs (edited 1/18/2012 7:53p).]