Re: Ukemi worried
Don't worry about it. It comes with time & practice...like every technique. I'm relatively new to Aikido myself and I still struggle with ukemi. However, I'm getting better. Just don't rush it...be patient. The single most important thing to remember is to not take a fall unless you're comfortable with it and you have been given plenty of hands-on instruction on how to do it correctly. Contrary to what a lot of Aikido detractors claim, Aikido can be a very dangerous martial art. You can easily break any of your limbs or even your neck if you fall on them wrong.
Your profile states that you're still deciding upon a dojo. If that's still true, then be sure to shop all local dojo. Be sure to look for two things:
1) Is safety emphasized and is it observed? Does it look they're learning a technique, or does it look like they're trying to "show off" and/or hurt each other?
2) Observe the students' behaviour. Do they look like they're enjoying themselves? Do they appear to be scared of the instructor or some of the other students?
Chances are, if by observing a certain dojo and you feel uncomfortable just watching, then that's probably not the place for you to begin your training. The dojo class you observe where you just can't wait to step on the mat and join in is the place you need to be! Trust your instincts.