FWIW, Kannada
is my wife's mother tongue, and while she admittedly does not fluently read it, she
did grow up speaking it and surrounded by the language...
In the 3 1/2 years I've lived in India - all but maybe six months cumulative in Karnataka - I found I mistook Dravidian scripts for one another as often as I got them right.
Here's a link to the syllabic characters of the Kannada alphabet:
http://www.omniglot.com/writing/kannada.htm
ETA: Considering there is an unquestionable similarity to at least a couple characters in the inscription, maybe another dialect or colloquial language that borrows from Kannada script, e.g., Konkani?