No. We allow the same languages as the World Finals. Allowing additional languages would cause more work for the Site Coordinators (who must install the necessary software) and the Regional Chief Judges (who must write judging utilities for the language). Also, there is a fairness issue: programs written in scripting languages like Perl and very high level languages like Haskell are often an order of magnitude shorter than programs written in traditional languages.

Programmer skill is more important than the choice of language. However, all other things being equal, Java and C++ are the best choices because of their large standard libraries that contain data structures and algorithms not available in C or Pascal. The World Finals holds a Java Challenge in addition to the regular contest, so that might tilt you in favor of Java. Pascal is dying in the United States, and may be phased out of the regional competition in the future.