There will be supertitles, but the thing about opera is that they repeat themselves a lot. So it's not like watching a foreign film, necessarily. Once I sat in the first row at an opera so I had to lean back to see, but fortunately I didn't have to look up that often. I would look at the story so you're familiar with it, too, though as others have said La Boheme is pretty much just like RENT, only no one's homosexual (okay, that we know of

), Mimi's a seamstress and not a stripper, and it's TB instead of HIV.
My recommendation is to be familiar with the story, and bring opera glasses or binoculars.
Also--a lot of times with arias, you think that it's over when it isn't. So don't start clapping until you're sure.
Jimmy, what are you doing here in the middle of the night? It's almost 9 PM!