Absolutely. I was mentioning it on RGP for the first few days, but so many people signed up and posted so much so fast, I thought I better cut back for a while
There's also currently a problem with some people getting the registration confirmation emails... I've been trying to get that resolved too.
But sure, you can do whatever you like. I'll ask that you don't spam it annoyingly, but if you like it here and want to tell other people about it, go for it.