FIRST has TONS of promotional material. Check out
http://usfirst.org/roboticsprograms/...er.aspx?id=952 (it's hard to find, I don't blame you for not being able to find it)
When you're recruiting, it's important to mention that EVERYONE is welcome, and they will have the same opportunities as the upperclassmen. In your case, be sure to state that there aren't a lot of upperclassmen to fear in the first place. If you introduce new members to the fun of FIRST in the beginning, they'll more than likely stay until the end. Don't just host team safety training sessions, host training PARTIES. With rewards. Get them dancing and laughing early on. Nobody likes to wait for promised fun.
Finding the balance between recruiting the geeks and wrangling the non-engineers is really tricky. We've tried for years to promote "it's not all about the robot, we do marketing too!", but we've been unsuccessful. It may be due to the general area's attitude and culture, or we just might not be strong enough. Right now, all of the PR and marketing type jobs have fallen to the team captains. Having written most of our Chairman's award and staying up until 3am to edit our video, I give you some serious awesome points for doing it all yourself (has your team considered you for a Dean's List nomination??), but that's definitely not a job that's designed for one person. I think that the best ways to try and attract those students are a) recruiting through friends ("Hey, you like talking about your toy horse collection, I think you would be a great person to talk about our team at competitions and team events!") and b) actually SHOWING prospective team members that PR is fun, and that it exists. Take videos of students talking to judges, sponsors, and other people. Be sure to promote what you DO, not just throw out titles and responsibilities (if that makes sense).
Note: I had originally joined my team because I wanted to make necklaces and use Photoshop. I've ended up doing just about everything except programming/electrical...and making necklaces and using Photoshop. Keep in mind that not everyone does what they come out to do
$0.02