Yes it is hot on the ground in summer. Some strategies, depart and fly early in morning. Keep plane in hanger and shade and preflight there, and get in and go, with out "Toiling on the ground" in direct sunlight and hot ramp. The AC is going to add weight, using it or not, it will be there, to rob you of takeoff, climb, cruise and range performance. The "no free lunch" rule comes into play.
Have you flown with AC in a small plane? The report I heard (Bonanza driver put one in) was the outside temps were in the 90's, plane was heat soaked and the AC did not do much to cool the cabin. It did help, but not the panacea you might think. Start with a mildly warm airplane and temps, yes it will cool if given time. The TRICK is being able to run AC on electrical GROUND POWER before you get in for an hour or three (in the shade). No expert but I believe these AC unites max BTU's cooling are just enough to maintain temp in extrem conditions (again see advice above). Keep in mind to really work at all you need to have insulated upholstered cockpit (more weight).