I would think that if you plan on practicing in hospitals, be VERY careful about who you choose to show effects to. People who may not look like they are in pain, in turmoil or whatever, may actually be the worst people to approach.
I had a broken finger recently (the summer), and while in the waiting room of the ER (before you get called over to get X-rays and stuff) was in a lot of pain. If anybody were to have approached me at that time (me looking pretty much normal despite a swollen finger which can be easily overlooked), I would not have been receptive to them at all. That's despite me being a magician myself.
That being said, if you politely ask them if they'd like to see some magic, then you give them the option to either decline or accept. Be very ready to face a lot of rejection. The people in the ER are there for a reason, and most often it is a very bad reason to be there. So be careful, and do not care about somebody telling you to go away.
Now, in the case that you plan on practicing in restaurants, bars, etc., I really hope that you've practiced routines and patter at the very least to get your presentation up to par. DVDs like "Live at the Jailhouse" are essential for someone beginning in this field. Performing at a restaurant or bar isn't as easy as simply walking up to someone and showing them one or two, non-routined effects. You are a reflection on the restaurant itself, and if you give a bad performance, you may lose business for the restaurant.
You've been warned previously in this thread to be prepared for rejection, and it seems that you've already faced some. So it is a good thing that you're going out there and trying your best to get a gig. However, as I've already said here, be VERY prepared with your magic, and be VERY prepared to perform even when you do not want to. It will be necessary for you to keep going down this path.
Hopefully some of what I've said is helpful, then again, it might not be. I'm just trying to make sure you're fully prepared before you go out and practice on real spectators. Good luck, I hope you do well.