Me and the wife ride ours around town the most and they are good enough for that with no problem just stay off the expressways.
We have ridden them offroad and while I do fine with mine my wife just can not ride hers in the sand and I must confess they are a handfull in the sand.(but I like it) I did manage to ride hers up a rather large sand hill several times a couple of weekends ago and they will do some decent offroading for what they are.
You will have no problem keeping up, moving with traffic even if it's a bit hilly (they are 5 speeds you know-
)
The engine mounts are a very weak spot but can be taken care of relatively easy so thats not really a problem.
Drum brakes should work fine and in fact may be better than the disc brakes since the disc brakes tend to want to lock up somewhat randomly until adjusted just right.
Drum brakes only fail badly when you go thru deep water and basically they dont work for a little while until some of that water gets out of there.
(I'm talking a deep river crossing with drum brakes submerged then up on the throttle into a quick stop type of thing)
Washing the bike or going thru a puddle wont effect drum brakes at all.