Popping in, since I'm here ... I think the only folks who have a reliable count of locations used would be Russ's team. He has a binder that lists everything since season 2 (when he took over as location god) and includes most of season 1 as well, and there are literally THOUSANDS of places! Jerry Wanek and his crew are also wizard at redressing locations they reuse to make them look different, no matter how many times we see them.

Each episode has 8 days to shoot, and judging by the few episodes for which I've seen any production documents, half or more of that shooting time may be spent on location.