Brian, Part of the difficult is that the SQL is illustrating a "code smell." That user id column really should be a separate table. That table myTable would have a primary key that is used in the user id table.
Assuming you can't change the schema, the best SQL query depends on the full SQL query. For example if we are querying by first name, the five joins would be good because that is the most restrictive filter.
If the most restrictive filter is on myTable, you could do a union and one big join. select cols from (select cols from myTable where ...) t1, (select cols from myTable where ...) t2, ... (select cols from myTable where ...) t5, userTable u where userid = u.user
It also depends on how expensive a join with the users table is. If it is a small table, it is unlikely to make a difference which approach you need.