Both MSLP and Denver are rather large airports. Chances are if you're making a connecting flight with the same airline you'll be in the same terminal.
As for time between connecting flights leave a couple of hours between the two. You need to plan for unexpected delays such as weather or mechanical problems. If you're late getting into the connecting airport airlines don't very often wait for connecting flights coming in late. If for some reason you miss that connecting flight you're put on standby for the next one - that is, if the flights are full.
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