Assuming the Enclave hasn't been killed off....
Yeah. I would join. Why? Well because I'm selfish.
The Enclave has access to great medical care, highly advanced scientific knowledge, a clean warm bed every night in a safe and very secure location, access to highly mobile transport (vertibirds), and a soldiery who are highly advanced, trained, and strong enough to defeat virtually any threat.
I'd just be a peaceful scientist and tinker away at computers or whatever safe inside whatever government facility we were staying in.
Edit: Just realized this was an in-game question. Not a "if you were dropped in the Fallout world" question. Still, some of those points still stand.
Correction: he was written poorly, like just about every other leader in Fallout 3.