Where did you get your tablet, and what version of the OS are you running?
There are different builds for different markets. It might be related to that.
My USA tablet purchased directly from Acer USA only had 4 languages, but I think the EMEA version has more.
If you are asking about the menus in the applications that's up to the developer. I don't think the Android OS comes in Hebrew unless there is a custom ROM for it..
Check out the website 'FrumHacks' they have all kinds of information regarding Hebrew on the Android tablet. according to their site in 2010 they have used a version of Android Froyo 2.2 that they claim supports Hebrew. Not sure how active their blog is though....Out of curosity, I just did an internet search for Hebrew on the android tablet and found it.