G'Day
I don't think there is one PSI call that will provide you with the list of
valid projects for the user.
However you can code around it. I would: -
Using the Project Web Service
1) Read List Of Projects via ProjectDataSet.ReadProjectList
Then For each Project returned
2) Read the list of team members via ProjectTeamDataSet
ReadProjectTeam(System.Guid projectUid)
3) Check that the user is in the returned list. If so Add Project to your list
Let me know how you get on