it depends what you want to say about them. Assuming it's not libellous (or even just derogatory), or malicious, you can say what you want; they won't be able to sue. But are you worried about the law, or just about being nice about people? If the latter, you might not want to repeat things said in confidence or snigger about someone's dress sense. But a straight, serious but uncontroversial account of things that happened to you should be okay.
Conversely, giving everyone pseudonyms would be pretty pointless. How many autobiographies would people read if nobody in them had their own name?
I'd set it in anything that left space at the end of lines or between lines for editors to write suggestions in. About 12pt-14pt seems to be normal in typescripts I've read, and any common, easy-to-read font. No messing round with Comic Sans.