I don't deny there are a whole lot of Spanish-speakers, but I'll say again that it depends on what you're going to do with the language.
I've never needed more than Sesame Street-level Spanish because I don't live in a area with many native Spanish speakers and I've only been to Mexico once, really. (Tijuana for an afternoon doesn't really count!) Since that trip was to Cancun, the tourist trap of Mexico, no Spanish was necessary even then...only dollar bills.
OTOH, I've been to France 3 times (once for a month), Quebec once, Germany twice (once for a month and once for 2 weeks), and Austria twice, so I've used my knowledge of French and German quite a bit. I also used my German a bit in Italy and Iceland when English didn't cut it for various reasons.
Spanish is certainly more commonly spoken than French or Latin (duh!), but it really comes down to what you want to do with it and where you plan to travel.