It really depends on how dense the crowd is and whether or not the room reflects the signal, and how far you are planning to travel.
If you dive deep into a crowd and are only 20 or 30 feet from the receiver you will probably be ok in most cases. If you really want to be safe just use a short length of antenna cable (availabel on our website) to put one of the antennas up a little higher. you will also need a bullet style BNC turn around which you can get for a couple of dollars from any Radio shack.
Wanted to provide an update... I purchased the G50 system. Did my first gig with it last Saturday and everything worked fine. It was a 4 set night - used the wireless for a full 3 sets (approx 45 minutes each) and 3 songs from the 4th set. Battery life indicator on receiver only showed down 1 LED at end of night (turned transmitter off when not in use). I did one trip into the audience... probably 50-70ft around the back of the bar and return through a fairly thick crowd in spots. No noticeable drop out. So far, I'm a happy camper.
I did get an extension for one antenna so I could mount it a bit higher up (on mic stand)...