Actually, I think E&M is more interesting than Mechanics, though it's harder (so I would recommend doing both). It's very possible to take only Mechanics, though the course would last only 1 semester.
My school only offers Mechanics, and it's supposedly THE most difficult class on campus. I don't really see how Mech and E&M can be combined into one year-long class without killing everyone who's taking it...
They're supposed to be combined into one year-long course. I don't even know how one might spend an entire year studying Mechanics unless your teacher taught you thermodynamics or nuclear physics or something like that as a supplement.