DO IT. I got back into BMX (both racing and street) last year and it was the best decision I've ever made.

For $350 you're not going to get a full chromoly F/F bike, unless you pick an older model up off of craigslist or something. If you can up your budget just a wee bit to around $425 you can get the Mirraco 20Forty which is a great bike and has a full chromoly frame and fork with a lifetime warranty. I ride a 20Forty. Haro, Diamondback, Felt, and Free Agent all have 24s at around the same price point as the Mirraco, but I think some of them are only partially chromoly. Above that is the Stolen Saint and Mongoose Thrive, and above those is the Sunday Model C.

Check out this thread I put together over on Vital BMX:
http://www.vitalbmx.com/forums/24-In...pletes,1263986