I have stayed at CG and it is very nice. Across the street from the beach with a small pool but shares amenities with the Best Western across the street. It is solely a BG resort and as such, cannot be reserved more than 11 months in advance. It only has 1 and 3 BR units and only has Friday and Sunday start days. I'd say the chances of getting CG for July 2010 are slim to none with RCI, actually pretty slim for BG members reserving directly unless Premier members as a minimum. If you want a 1 BR, I'd consider Sea Glass across the street as it's ocean front and BG currently only deposits the larger 1 BR unit there, which also tend to have the better views, last I heard. Personally I'd try to find someone to work a direct trade for the Marriott. For a 2 BR, I'd consider Shorecrest I in North MB. I know Wyndham has several resorts in the area but don't know any of them.
Tug is a good option, for BG, the yahoo BG groups is likely better.