In some areas the sea is advancing, swallowing beach and everything unprotected. Some friends of mine bought an apartment near Recife, and their beach... is gone.
In Olinda it's easy to see the struggle to sustain the sea. To win or to loose? If you plan any kind of investment pay attention to your chosen area!
The guides are very pushy, and in cahoots with the taxi drivers. Even travelling on the meter my taxi beeped to alert these guides who swarmed over to the cab. Helpfully, the cab driver dispatched those who did not speak English, then let them accost me with offers of help. The guides in a casual uniform will show you their ID badges and say they are "Official" guides and then haggle over their price.
The Brasilians are well aware that tourists can run into trouble and provide tourist police if you have too much difficulty. I did not need this service, but it is a comforting idea.
There are guides all over the old town. Among the independents are many who speak little (or barely comprehensible) English.
Using my indispensable Baedeker, I had no need of a guide (though I did allow a 'guide' of sorts to attach himself to me in the wonderful church of the Convento Sao Francisco).
If you visit Olinda and do want to be shown around, the best bet is to visit the Tourist Center. Student guides available there work for free (or for tips) partly to practice their English.
The Center is located on the ground floor of the Olinda Public Library on the Praca do Carmo, and offers a fine map and 'Guide to the Churches of Olinda' in Portuguese, English, and other languages.