I give the old folk's homes a solid discount on my fee, because even in America these places are on a tight budget. They can only spend so much in entertainment and that allowance isn't real high. Most all of the entertainers that I know cut a good deal to the old folks homes. Really, if things work out properly, we are all headed there so we might as well sow a few good seeds in that area (karmic law being respected by even the less religious among us).
I'd like to deal with this, though (from the opening post):
...all they do is try to figure out how the tricks are done, or not follow instructions.
First, learn to routine your material. If you do three or four effects in a logical progression, your audience won't have time to figure out how you did what you did. By routining your material, the strength of the overall grouping of tricks rises exponentially, which is exactly what you want. You simply don't give your spectators the chance to question what you've done or how you've done it before you are onto the next part of your routine. Much like cups and balls - when one ball disappears then impossibly reappears under another cup, the human mind accepts the vanish no matter how implausable it is. If you simply stop at the vanish, though, it is then that the spectators try to figure out how you made the ball vanish. This is important psychology to study.
As far as your audience not being able to follow instructions, this is your fault not theirs. Your directions MUST be clear and concise. The wording of your instructions must be in simple english and easy to follow. Keep in mind, it isn't communication unless both parties involved understand exactly what is being said. So, when giving instructions, without being condescending, you must make them simple and easy to follow - as if you were working with a 5 or 6 year old.
Further, this is a matter of audience control. This comes with time and experience. So, when you are having a problem with your spectator not following your instruction, pay attention to where you are going wrong. Later, sit down and work out a different way of instructing your spectator. Write the instructions down and study this part, learning your direction word for word in necessary - yes, this is work. But, if you're not willing to put work into this, then you should avoid any trick that requires this kind of magician/spectator give and take.
Mike.