If you're in a Cuarto suite, a 27" will be more than fine. Castillian area has large rooms; not sure of Thoreau/Webster.
Regan, you're probably better off watching TV on your computer. Regan has the smallest rooms, I believe, withe quads being the size of a single bedroom at Castillian.
If you're at Segundo, a 27" will be cramped. Same with Tercero. There's space, but you'll have to raise your bed or bunk.
If you're at Primero Grove, you have plenty of room for TV. Those are apartment style.
At Cuarto and Primero Grove, it'd be better to share a TV with roommates. The common area is large enough to seat everyone comfortably.
Everywhere else, it's probably better to use the lounge TV's or invest in a TV tuner for your computer.
If I were you, I'd forget about the TV. Freshmen year is pretty much the only time you can build your social network. It's also the only time when you can afford the spare time for it. If you're an engineer (I assume so since you're posting in AT) the difficulty level scales exponentially.
Good luck and welcome to Davis. The city with nothing, but only an hour from everything.
Oh, and one more thing. If you're an engineer and interested in pursuing a Master's or Ph.D, go to the College of Engineering office at EUII (Kemper Hall) and ask about undergraduate research. You'll have a serious leg up on everyone else.