temp tables in functions?

Having developed a complex query, I want to wrap it up as a function
so that it can take a parameter and return a set of rows. This query
is currently written as multiple sql statements that create a few
interstitial temp tables that are then joined. If I put this into a
function definition, do those temp tables get dropped automatically
when the function returns?

My alternative is to re-write the query as a self joins and
subqueries. I can do that, but it's somewhat less readable.