Cycling shoes have stiff soles so unless you're walking very short distances, I'd plan on sticking a small pair of flip flops in your seat bag or jersey pocket.
Shoes need to fit - period. Don't go by brand names. Know that your feet will swell with the heat so be sure that you can wiggle your toes.
A really nice pair of cycling socks can be heaven. They wick sweat and keep your feet happy.