Just as most users don't know about Ctrl+, most users wouldn't know what "adjust text size up / down" meant either. My 60 year old father uses the Internet a lot, but he wouldn't be able to identify your use of the word 'text' with the words he reads on a website. Up or down to him would mean scrolling.
That's interesting. How else would one describe the words that you read on a website? It's text. Or copy. But text is probably more universally understood.
If he were reading a magazine and you said "do you find the text to be too small", you think he might turn to you and say "what do you mean by text, I'm reading a magazine here, there is no text."
