You can forget trying to js on Volaris. No Mexican airline allows jumpseating as we know it. Showing up at the gate and attempting to get a free ride on any non US or Canadian airline is unheard of. They won't even know what you're talking about when you tell them you're trying to jumpseat.
Your best bet is to jumpseat on an American airline flying out of Mexico. Try Continental / Expressjet, Alaska, AWA/USAir or DL out of PV. American won't allow you to js on them internationally unless your airline offers them an int'l jumpseat. Good Luck.
It was two years ago. After listing on-line and trekking 2 hours to JFK, I was greeted by friendly agent informing me that my former airline doesn't do international with AMR. Needless to say I didn't get to CUN in time for Happy Hour.
When I worked at XJT we had a couple guys that lived in Monterrey and commuted to Houston. You can't ride in the cockpit so you need a seat in the back, and you have to pay taxes to get into the country. I think they paid $30 each time they came to work. The one guy I knew only paid $150/mo for a nice apartment with a maid who did his laundry, so the $30 per commute wasn't that bad. It's probably a little tougher if your trying to do it on OAL's, but you could do it.