Housebreaking

Question
I have a boxer which just turned 3. For a while he seemed to catch on to house training, but then started peeing in his cage.  I constantly scrub the cage and give him "new" bedding. He also seems to pee anywhere else he can.  If we are sitting with him, he will not pee, but if I go to the bathroom for a second, he will pee (on anything) and its obvious when I return he knows he was bad. He will hide or run away.  When I take him to the pet store, he will pee on everything.  When I let him out to go to the bathroom he will pee on every bush, flower and tree all within 1 minute then will finish on my 11 year old dachshund.  If he sees me watching he will not pee on her, but if he thinks I'm not around, he'll go for it and then I scold him as he starts to lift his leg.  He has peed on the neighbor's deck and the neighbors dogs.  Even if he has no pee left he will continue to lift his leg on things and try to pee.  I love him, but don't know how to handle this problem.  Please help!

Answer
The first step is a vet visit to check for a urinary tract or kidney infection.  The marking is not unusual, especially if he's not neutered, but peeing in his crate is a sign that something else is going on.  

If the vet rules out any medical issue, it may be psychological - have you changed routines, added a new family member, etc. lately?  If that's the case, going back to basics on housetraining, and establishing a daily routine so that he's more secure, can help.