Just to update this, Firefox mobile, like Fennec, now runs on high-quality Android phones and supports webgl. Some of the demos will run a little slow ... this is the case for most 3d processing.js code, since it doesn't seem to use highly optimized webgl. Some of the demos, especially those written in thin layers of webgl frameworks like spidergl, work pretty well.
Your Android device must support the arm7 instruction set to run Fennec. This excludes junior class phones, but the Evo class, tablets, etc. Will work fine.