It's a question I've been asking for a while.
The short is is no, you can't use Hebrew.
AGK only support Windows1252 encoded ASCII but for Hebrew you will need full Unicode support.
There is a possible workaround that I have been using to support Russian and Greek text that might also work for Hebrew although the right to left will need some additional tinkering.
What I do for Russian and Greek is this:
I have all of my text in a text file that is read in at run time. That's the same for all languages but those that are not supported by Windows 1252 get some additional preprocessing so that the characters are remapped.
I have an UltraEdit script that runs through each file and converts each character to another that is supported. So for example a Greek Omega is remapped as a Q or ascii 81. A Greek Pi is remapped as P or ascii 80. It makes the original text file totally unreadable but once it is in AppGameKit it can be read and as long as you know which letters are remapped to which (obviously you do!) then you can create a bitmap font accordingly.
It's far from ideal but unless AppGameKit is changed to support anything other than English then workarounds will have to be used.
AGK V2 user - Tier 1 (mostly)