The PackedTextMesh shader doesn't support GLES 1.1. I think it is possible to port it, but I don't know how many actually use this shader - it is an experimental feature after all. If there is demand for it I can obviously work on a port the shader.
If you can wait, I suggest waiting for the next Unity. Unity are dropping support for GLES and apparently have made the GLES2 codepath as fast as GLES1.1 path - that will probably be the best thing to do.