You'll get a better germination rate if you start with pots of seed starting mix, if you do start seeds. Sowing seeds directly in the bed is more risky, considering weather variations, wind, bugs, birds and other hazards seeds and small seedlings must survive.
If you can find somebody with some Mex. sunflowers already up and going, they start really well from cuttings too. That might give you a head start. Just root the cuttings in water, or some perlite and water, then when you see new growth starting, plant them out like regular transplants.