I don't know about other groups and I'd love their opinion, but I know that our group gets a lot of email from folks asking if they can go on investigation with us. The simple answer is "No." I'd say other serious investigators, maybe. The average person out there wanting adventure and excitement ghost-style. No.
You'd just be surprised how little people pay attention to notices on websites. I'm pretty helpful and don't mind answering questions and helping students with papers and stories. But, when you have a notice saying we're not accepting new members and investigations aren't open, it's always a little like "Whaaa?" when people ask anyway.
Guess it can't hurt to ask, huh?