Do WWE really edit out John Cena booes? Do they really confiscate 'CENA SUCKS' signs at events?

No way to prove it unless you're at the event and then watch it on TV later and notice a difference. I would say that it probably does happen, since the WWE security guys do take signs away from the crowd, and they have pumped cheers and/or boos in before, more or less on Smackdown, where they can edit that stuff. Kinda hard to edit a live RAW.