... don't worry about playing in your back yard if you're in a rural area, as long as you abide by your municiple and federal laws - you will be ok.
If by chance a police officer does come by - treat them with respect, put your safty on, take the magazine out, put the airsoft gun on the ground, step away from it, place your hands in the air, and follow any directions the officer gives you. Do not say anything about it being an airsoft gun, as it may be confused with, "It's just a *** gun!".
As for the Broxa, I've seen 3 come in to my area and I think there's one left in operational condition. It's up to you what you want to spend. Parts for repair are available everywhere. IMHO with limited funds and general skirmishes, I'd buy it.