You are very unlikely to run into fighting bulls. You may find half-bred fighting cows, and they can be nasty, but only if you stand between them and their fresh born calves. This is the theory. Then, when you see a group of black as black can be cows running towards you along a dirt track, you start looking at the best fence you can jump over, but if they are moving between fields, they will be accompanied or lead by their cattle herders, you should have no problem. If all comes to all, as when you are facing a horse that is gone rogue, when they are running to you, just stand with your legs astride, and wave your stretched arms up and down (better if you have a stick) and shout at them, and they should avoid you alltogether.
This said, chances are you will never need to use that last resource, just wave your arms on your side up and down with plenty of energy and shout something nasty at them, and they will avoid you. And never get between a heifer and her newborn, that is the key!
In october, you should not find so may fresh born calves, in theory, calves are mostly born late winter/spring/early summer