When I was about to have my surgery I spoke to a woman who'd been wrapped two years prior. I was lamenting the fact that I wouldn't be able to drink beer due to the carbonation.
She said, however, that beer's carbonation is far less potent than soda carbonation, and that she'd had no trouble at all drinking beer post-Nissen.
That said, at the early stages of recovery when bloating is more prevalent, I didn't do more than take sips.
However before the 6 month point I was drinking a beer with no problem, and I continue to do so. I can't pin down the exact timing though...sorry.
Happy St. Patrck's Weekend!