Hey Canadien
Definitely got to go with NorthSides and Spot1s advice. It is definitely the best way to go if you want to progress quicly and improve fast. Get a surf lesson from a licensed surf shcool from that particular states governing body. for example if you are in Queensland a Surfing Queensland Surf School, or if in Victoria, a Surfing Victoria Surf School. Going to these schools, you will have confidence that they are properly accreditted, know what they are doing, provide superior quality and high standard service and will do the right thing by you. i have found that some of the 'independant surf schools' can be complete cowboys and don't do the right thing by the customer.
re board size - The other guys probably have not had much experience surfing themselves or getting others going. You can do it their way buying a short board and goign from there but your progression will be really slow and really drawn out. More than likely you will give up the sport before you have found out how much fun it realy is. When you are learning the bigger the board, the easier it is, the more waves you catch and the more fun you have. if you get on a board too small too early, you sit out the back, watching others catching and riding waves, hating being out there, getting frustrated and not enjoying what should be a really enjoyable sport. This is the reason why surf schools use big boards and why they recommend that if you are going to contiune surfing, stay on a bigger board for longer so you can nail your technique and then begin to down size. This way you will find out how good our sport really is!!!
good luck with your surfing, hope you love it!!!