No, you should not preprocess the dataset. Depending on the tokenizer scheme, you may want to tokenize words beforehand (which will then still be tokenised into subword units). For something like sentencepiece that is not needed (in fact it is recommended to not pretokenise in sentencepiece because a space is a regular character there).
It is best if the data is “clean” though, in the sense that it should not contain HTML/XML tags or other longer sequences of strange characters. But that should then also be true of inference data.