Our team recruits at freshman orientation, before school starts. We bring the previous year's bot and show it off. Basically, people come to our table because we have a huge robot rolling around the cafeteria. If people approach, we tell them briefly what we're about. If they're still interested, we get their name on a sheet. This somewhat ostentatious display draws freshmen and older siblings to us.
Last year, we did presentations for the entire school to reach everyone else (I feel the pain, we have a small school too). We put together a PowerPoint about our team and FIRST and, of course, brought the last robot. Each subteam would sum up what they do, too, to show the diversity of things to do.
As for engaging our students, we share the stories we've experienced. We tell new members about some of the more extreme examples of gracious professionalism we've seen or performed. We rely on that and the engagement of the program to keep new members around. For the off season, we play at one off season competition every year (MARC). This and fundraising (like team car washes) keeps the team together through the summer.
I'm not quite sure what you mean when you talk about communication, but I'll try =) We have a full team meeting at the beginning of each meeting/practice. Here, our mentor updates us on important information and the students also have input. Our team captain also has all of our phone numbers, so the night before something important, he'll send out a group text to remind us. If someone manages to completely forget something, there's no "punishment", just a healthy chewing out from the whole team
Unfortunately, I'm not in any position to talk about mentors. We have one mentor who has done it for ten years. We have not had an engineering mentor in
many years. We recruit for mentors at the local nuclear power plant (which we are just lucky to have five minutes from the high school). This year, a former team member came back to help out. We are grateful for any help and we manage perfectly fine without an engineer. I think it motivates, actually, but I certainly wouldn't turn one down!
I know this is long, but I hope I helped. Feel free to PM me if you have any more questions!