Maybe I'm delusional, but I can't really ever remember the rain being overly bad in October. Right now is the rainy season, not October. October is when the rain has dissipated a decent amount, and the weather begins to cool down a little.

Then again, it seems to be different every year. This year it began raining every few days back in February, which is much earlier than normal. However, last year it didn't start raining daily until around June I think, which is way later than usual.

Nonetheless, unless there's floods or something, I can't really see rain hampering an enjoyable time much. Even when it rains, it's still like +32C out, so it's hardly uncomfortable.

EDIT: I don't personally do this, but if it's raining, may want to wear shoes instead of sandals, especially if you're walking around markets where things like raw chicken and pork are being sold.