Where to go, and how to renew your visa by yourself in Cebu;
First of all go a bit respectable dressed, no t-shirt, shorts and slippers, wear trousers and shoes at least, up to yourself, but to be turned away by the guard is no fun at all, and if you have to do it THAT day, to give the touts outside big money to borrow some clothes and shoes for a while, makes no sense at all!
For your DIY visa renewal you can go to 2 places in Cebu, in Mandaue, or in Mactan;
The Mandaue map will follow soon.
In Mactan /Lapulapu, near Mactan Airport you can go here , there is a lot more good info on that website, about how to get around in Cebu city, by taxi, jeepney or walking!
Well at least shops to buy shoes and pants, are right there beside you.