I will say, and I'm not the only one, that upgrades depend more on where and when you're flying than on your status. The others are right that (mainline) flights touching DFW are very hard for upgrades, so unfortunately for OP the chances of a First/Business class upgrade on that trip to SJO are slim to none.

On the other hand, though, it's fairly common for everyone on the upgrade list to clear on short regional hops not touching DFW. So if OP has another shorter trip coming up, they may well end up in First Class.

And yes, the complimentary first/business class upgrades are only for flights within North America.