The vet called this morning, and based on what the ER vet faxed over and what we told him about this morning, he's positive it's a UTI. Beans has been dribbling a LOT all night (the first one was with blood - we watched him - but the ones after that weren't) and peed a pretty substantial amount in the sink, without blood.
I've been up all night listening to him cry and scratch at the bathroom door. I may call in at MCHS and ask to come in the afternoon so I can get more rest.
I'm sorry I was SO freaked out last night... we knew a cat (we pet-sat him) who died right in front of us... and the autopsy said that he had urinary blockage. So that's all that was in my mind last night. But since his bladder was mostly empty before, and he's been able to pee a little since then, I think he'll be okay with the antibiotics. But the vet said to take him to the ER vet immediately if he's showing signs of straining with no pee to show for it.