I just did a six day tour of Croatia, Montenegro and Albania (where the next SPG property after Split is located) last week. I would avoid Zagreb unless you have a particular reason for going there. Split is the nicest of the Croatian SPG properties.

I found the Sheraton in Zagreb to be a bit run down. In the Standard Suite the touch of painting on the walls was done in a different color that the original coat, which I thought was pretty poor.

If you can fit it in, I would recommend heading down the coast of Montenegro - it is quite picturesque and less crowded than Croatia. The roads are good quality, although I do not think there are any super-highways.

About the casino and the club in the hotel - they seem to only open for high season. While I was there last week, they were certainly closed.