I don't think the Tiagra rear derailleur will handle a 32 tooth cassette. They are designed for a top end of 27 teeth. Some folks have managed to make it work on 30 tooth cogs, but 32 might be pushing it.

If you have to change the derailleur to accommodate a 32 tooth cog, why not put something like a Shimano Deore rear derailleur, and an 11- 36 tooth cassette. It will not cost any more, but will give you a bail out granny, just in case you cycle somewhere besides Florida. In a 3 week ride around Michigan, a supposedly flat state, we gained a total of 31,000 feet. Bikers know that there is no such thing as flat!