Good timing Prawndog, hopefully we'll start getting the daily sea-breezes here in WA soon and meanwhile you can sort up the gear.
Most has already been said, and yeah, the learning curve can vary a lot depending on your inherent ability. I've always recommended to start with a big floaty (>80 cm wide, >200 L) and a comfortably small sail (5 m2), this allows you to focus on the basics without having to worry about keeping yourself on the board. I know this is a controversial topic, as some have managed to learn straight from smaller boards, but in my experience these are more the exception rather than the norm.
If you already have kiting or surfing background you will definitely find it easier, and may be able to start getting a taste of the windsurf-awesomeness right this season.
I windsurf all year round and I cover my sail needs 98% of the time with 4.7, 5.2 and 5.6, combined with 100 L and 85 L boards (3 sails + 2 boards). The other 2% of the time I may use the 4.2 or 3.5m2 sails for the wild winter storms.
You may also want to check the new-school freestyle windsurf, it is a mind-blowing discipline... still focus first on the basics!!