I can play alto, although I mainly play tenor, but I've decided that I like alto MUCH more. I just would like to know if there is any major differences I should be aware of between the two sizes-embouchure? Notes to be careful for(such as the D on tenor)? I know Alto is in E flat unlike tenor's B flat, so now I need to go over which scales are the "concert key"...what fun. Anyway, I appreciate any help!

Its not hard about key just remember when you play a C it sounds like a Bb concert key. In other words if you are playing a concert Bb scale your playing a C scale, only one whole step up. (Its actually a 9th but that doesn't matter when playing scales). All saxophones have their different quirks but you will figure them out.

like you, I am also a tenor player mainly. For pit band, I had to switch to alto, and it was really easy to catch on, honestly! Also, you might be happier with the weight differnce between the two. Good Luck
Beetlejuice
get a high strength reed for the high notes as well, and you will also tell that alto low notes a a LOT easier than tenors