You are probably lucky that the garage receptacle is on it's own 20 amp circuit breaker. Most homes have at least one or two bedrooms on the garage circuit breaker.
The laundry room typically has two 20 amp circuit breakers feeding it (NEC code since at least 1960). SO that is a great place to find a dedicated 20 amp receptacle when visiting someone. . .
The best place to plug in your 50 amp RV at a friends house is to use the electric dryer 4 wire receptacle. It has 120/240 with a neutral just like found in your 50 amp service. So you could run many things with that sort of adapter. It would allow up to about 7,000 watts before tripping the 30 amp circuit breaker that feeds the electric dryers.
You are also probably lucky that it is cooler outside today. ON a hot day, it can take over 12 amps per rooftop A/C unit, while on a cooler day, say 80F outside, then the A/C unit amperage is only going to be around 10 amps or maybe a little less.
Fred.
