Hi Harrysurfer,
There are only really a handful of good newbie spots in all of Perth. Melville is good but has gusty wind and no beach, and can get pretty crowded. If you go there, stay downwind of the main crowd.
Pinnaroo can be busy, has large chop in strong wind, deep water, and during holidays, loads of other beach users, a steep learning curve but probably one of the safest spots around (especially if we're there with the boat to help rescue when things get ugly).
Mullaloo is good but they also have issues with the public and the flagged swimming areas. Can have some nice small waves to jump off.
Peli point isn't an ideal learner area as there are so many sensitive issues there including but not limited to bird conservation area, pedestrian pathway, no beach, rocks etc.
Woodies can be ok on the onshore beach, but going downwind can be a worry

Safety Bay is probably one of the best areas and works well in SE to SW. There are issues there too with some of the windsurfers, but it isn't as crowded as other spots.
All areas have their pro's and con's. It will probably be more determined by proximity to where you live. Get to know the locals at your closest beach and ask them where you won't be in the way. Remember, everyone was a beginner once and you are only a learner for a short time if you put your mind to it.
Good winds,