Yes mountains are bad during monsoons. They are risky because of downpours, heavy non stop rains cause landslide, slippery roads. You could plan to beach places. Also if you are interested in visiting hills of south India where not much rain prevails especially in the east side - Tamilnadu Andhrapradesh and Telegana you could check these places
-Ooty and Kodai
Valparai
Meghamalai Coonoor
Lambasinghi
Araku valley.