I can use the '=' and '-' keys on computer to adjust the font size in Google Reader, but can't find how to do it on iPad.
The best way I have found is to use the "Change Font Size" bookmarklet from lucidgreen.
Its a bit of a pain to setup, but once you do, it works great for google reader on ipad.
You'll need to have safari installed on your windows/mac computer. I've tested this with windows 7. And, you'll need to set itunes to sync bookmarks from safari to the ipad.
2) Search for "Change font size" to find the bookmarklet link
4) Run safari and create a new bookmark to any web page
6) Sync your ipad (remember, you must have checked the box in itunes to sync bookmarks)
7) Now when you go to google reader in safari on ipad, you will have a Change font size bookmark.
8) Choose the bookmark and it will prompt you for a size
10) Finally... Actually enjoy using google reader on ipad.
I can't answer your question about that per se, but I can say that there are much more elegant readers available that use Google Reader as a data store. Reeder is the nicest I've seen--very tactile and minimal and iPaddish and lovely.