my back ones squeal like crazy the first 2 times I use them that day. They don't make a sound after that.  The fronts never make any noise.

I'm sure the back shoes are stock.  Not sure what's on the front.  They were on there when I got it and still have good pad on them.

The short answer is "no", brake squeal is not common or normal. Here's the long answer...

If you have brake squeal, then something is wrong. Not wrong like don't ride your bike, but wrong none the less. Brake squeal is a byproduct of vibration - it's your pads vibrating like a guitar string. The pads should be loose when there is no pressure applied to the brakes, but once brake force is applied there should be sufficient pressure to transfer the force from the caliper piston to the brake pad without vibration.

More than likely the back of the brake pad - where it makes contact with the piston - isn't flat. Look at the pads for an indication of uneven wear. Apply some "anti-squeal" grease to help dampen the vibration, or change to a different pad. Less likely is an uneven surface on the piston or a piston that isn't being driven straight from the caliper. If this is the cause of the squeal then the caliper will need to be rebuilt.