Hi Melanie,
I checked the on-line calendar for Operational Updates for May at Disney Hollywood Studios. The only Operational Update currently shown is for Muppet Vision 3-D which is scheduled to be closed for refurbishment Saturday, April 24th - Friday, May 14th.
I would imagine with the 2010 Star Wars Weekends taking place May 21 - 23, May 28 - 30, June 4 - 6 and June 11 - 13 that they would do everything they can to have Star Tours open. Of course there is always the possibility that any attraction can close at any time for a number of reasons.
You can see a list of any scheduled Operational Updates for your trip on-line by checking the daily calendars for each park by clicking on the following links:
Magic Kingdom
Epcot
Disney Hollywood Studios
Animal Kingdom
That will take you to the current month's calendar which will list the hours of operation each day including Extra Magic Hours. You can change the month by clicking on the drop down list beside the
View Month box. From there, click on a specific date to see the parade and fireworks schedule. To the right of the times, you will see any scheduled Operational Updates. You can also call 407-WDW-MAGIC or 407-939-6244, to confirm any Operational Updates you see on-line.
Wishing you many magical memories :-)