Only one language for me. I do a few Cajun songs in French, but I do them pretty much phonetically. When I was young I could speak a little Osage, but there's not much demand for that!
My friend Vince Ramos in Houston speaks English, Spanish and Italian and sings in all three languages. I've been fooling around with an online Spanish course, but not devoting enough time to make a lot of progress.
I can do many hundreds of songs totally from memory. Sometimes I might mess up a line or verse, but not too often. No telling how many I could play without singing.
DonM