I'm going to check the rules about this. I'm fairly sure that your sig is fine, but they did tweak it a little while back, so I'll go have to check that.
Edit: Scanning the front page, it doesn't seem to be containing anything inappropriate, and I don't see anything involving PayPal or anything involving USD, so you're good advertising it in your signature. Just remember to keep within the limits and to not draw too much attention to it (*cough cough* SPAM THREADS)