can a 12v hobby box battery be charged with a regular (car/boat type) charger?

Sure can, At least that's how I charge my field battery, But I do use
the 2a charge... No problems in 9 months while using my auto charger/
maintainer about every two weeks...

Yes it can, the problem will be that at times, you need to get the battery to top out at about 14.5 volts. I could never get my car charger that high.

does it matter if its gel or acid?

I have charged both types with a standard 12 volt 3 amp charger with no problems. If its one of the high output chargers that puts out 6 amps or higher I would avoid using it. [8D]