I guess it was a typo when you said descend into left downwind, as obviously descending on the active side of any runway is generally a no no, the best way to come down from overhead I find is to descend and join a crosswind for the active runway.
As for asking which runway is in use, country folk are generally happy to help but I would ask for wind speed and direction instead of asking which runway just because it gives you a better mental picture so you don't find as many surprises on finals.
If flying to a strange strip I always prefer the overhead method just to get a good picture of everything but obviously if it is busy sometimes it isn't the best.