Should I disable autovacuum on a table while I do a bulk update?
No

There is simply no point. autovacuum will not clean up any rows locked in a running transaction. So autovacuum


may not do anything useful.
may report that the rows are dead and nonremovable
may do something useful with the other rows (if there are any).


But, it won't block or slow down the update in any meaningful sense that I'm aware of.