Thanks for the replies on this. I ended up hitting up Volaris on Twitter to ask them about the baggage transfer and they told me that Volaris will handle the transfer since it's under one reservation... that was not correct at all.

When we checked in at SJO airport, we asked them at the counter and they said we'd have to get our bags and do the drop-off. If I had listened to Volaris on Twitter, we would have been up a creek without our bags when we got to GDL.

We were lucky that our flight got in a little early. We ended up with about 2 hours and 10 minutes' worth of time once we landed. That was barely enough.

Some notes for anyone reading this in the same boat we were.

1) The FMM we filled out online would have been fine except we hadn't printed it back-to-back on the pages. Apparently, that's a requirement and that's what one of the employees by the immigration line let us know. That meant we had to step off to the side and fill the forms out again. There was no line at immigration so we were lucky there. Also, there was no fee.

2) Even though we had to take time to fill out the forms again, it didn't matter time-wise. Once we got through immigration and over to baggage, the carousel hadn't started yet. In fact, it didn't start for probably another 20-30 minutes after we had arrived there.

3) We got our bags and took them through the long and slow security check. Then we dropped them off in a section just after the check.

4) We then rushed over to security for domestic flights. Since we already had dropped off our bags and had our boarding passes, there was no need to check in at the Volaris counter. The line for security took what seemed like forever but eventually, we got through that.

5) We basically ran from there to our gate (still in terminal 1). When we got there, they were already boarding. But we ran to the bathrooms for a last pee and then boarded the plane on time.

So, 2 hours, even landing and departing at the same terminal is really pushing it and something I didn't like. Good luck to anyone else trying to make that happen! :-)