Am I right in thinking that as soon as you tick the box 'allow advanced text' your text will be saved as an image?

I want to use some fonts that I don't normally use, and need to know that they will be the same for everyone. Help anyone?

Yes, the text will turn into images when 'allow advanced text' is clicked.

Some advice though: I don't know how much text you want to convert into pictures and how much will remain just as 'text'. But search engines want to read text, not images, so it is not advisable to convert all text. Leave enough for the SEO, and make sure that most of your keywords are used in that remaining text.