When it comes to the city with the stone walls i just starve them out, fighting on walls is bad enough without those machete weilding devils around.
My glorious indo-hellenic army (4 indo-hellenic hoplitai, 2 indo-hellenic agema, 2 indo-hellenic peltasts, 4 indian longbows, 2 sereni) got really badly chewed up invading one of the other towns but that was due to me forgetting about the beefed up elephant stats.
"Ho there Demetrios! do not fret over those elephantoi one volley of our mighty javelins should send them to hades....err maybe two" (stamp.stamp.stamp.)