I've got a client looking for a site with both english and arabic content. is the best way to accomplish this by doing 2 joomla installs? if i choose arabic language on a joomla installation, will i be able to navigate and play the role of admin if i don't read arabic?
You can install the the template in English or Arabic and then add the Arabic or English or Arabic language packs for both the front and back end, so where ever you are on the site, you'll be able to choose the language you want to work with.
Note: Some people have trouble installing sample date when choosing a language besides English. Most have success with installing in English first then adding the language packs they need. If you're not using sample data, you may be OK, but in any case, you can add a language after the install and make it default for the front end, back end or both.
I suggest doing a test set up locally or on a sub domain so you can play around a bit.
It's a bit confusing to use at first but once you understand the basics, it's really easy to use.
Also Note: Consider which 3rd party components you'll be using. Joom!Fish is set up to translate Joomla's 'Content Elements', it will search your entire database for any content that is not translated in the Joomla core. Most 3rd party components are written to follow Joomla's content parameters, however, some have 'Content Elements' that fall outside of those parameters. For example, DocMan document descriptions, Phoca Gallery category descriptions. 'Content Elements' like these need additional files to be added to Joom!Fish so the content can be recognized and translated.
If it's a pretty standard site, you'd never run into this, but if you plan to add a lot of 'bells and whistles' check to see which 3rd party components already have the extra Content Element files you'll need.