Plain napha is about the best to clean the intercooler interior followed by soapy water. Naptha will get the little bit of oil out and soapy water gets the naptha out so you dont run rich first starting out. The outer surface can be cleaned with a commercial HVAC product called "Hydro-Balance" coil cleaner. Its a mild mix of hydrochloric acid and soaps and it etches the crud off the fins.
Naptha is packaged as charcoal lighter fluid, Zippo lighter fluid and many other small use fuels.

As for the A/C issue I doubt mounting the intercooler to the front will cause any adverse problems for the A/C system, the only time the intercooler is rejecting heat is under hard boost and even then I doubt the temp is going to rise over 40F degrees delta unless you are packing over 20 PSIg. Its a toss up really, the A/C system is only going to run at 140F or less because most R12/R134 systems will not withstand pressures over 175 PSI and that would be 200F or close. You would have to take in some really hot air and get the freon loaded with heat, low side pressures over 70 PSI to get to that point.

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