Larry:
You're a switcher. You know how I can tell? Because you're being paranoid.
This is what Windows does to people; it convinces them that their computers can be easily breached.
This is not true of a Mac. The fact that airport and bluetooth are on by default means *absolutely nothing* to your security.
First of all, your airport card being on is a RECEPTIVE instrument. It's not broadcasting ANYTHING. Nothing. Not one byte of data until YOU set it up to do so.
Same for Bluetooth.
Second, as chscag pointed out, even if you DID set up the machine to be broadcasting information, you would have to take SEVERAL deliberate steps to make any actual data on your hard drive available, AND STILL someone would have to know your password to get beyond the "public" (empty) folder sitting in your user folder. Access to ALL OTHER folders beyond the public one is locked by default.
In short, you're fretting about nothing. Your Mac is not going to get remotely hacked without you actively wanting that to happen.
That said, of course if you are setting up your own wifi network (ie broacasting the network's presence), you should encrypt it. Hackers can't get into your Mac, but on an unencrypted network it is possible for someone close by your home to "read" the data you're sending out. WPA2 encryption should be more than sufficient to avoid that unless you live next door to the CIA (then perhaps stronger methods might be needed).