Plant them inside towards the end of March for planting out in mid-May or whenever the threat of frost is past. If planted any sooner than that they'll be really leggy & hard to handle. They should bloom this year about July or August.
You'll get a mixture of open centered dahlias from these- you may not get exactly as pictured because dahlias don't bloom true to the parents.
You don't have to do anything to the seed except plant it- they don't need freezing or anything. You can pre-sprout them on a damp paper towel & then put them in a pot or you can start them in a flat of potting soil & then transplant them when they get a pair of real leaves. Don't put them out until after frost & be sure to harden them off first.

I would think that you absolutely would get them to flower the first year. But, in some ways they are the perfect flower for you because they are very easy to dig up, store and transplant somewhere else!

I am not sure what Zone you are in. If you ground freezes they would need to be dug up and stored over winter. If it just gets cold, you may get away with leaving them in the ground, particularly with some extra mulch. If it is really warm, then I would look for some tips on getting them to go dorment, I am in Canada so I don't know much about warm weather places and their Dahlias!

I got some seed from Thompson and Morgan. It looks very much like the white ones pictures above. It will be interesting to see how close the seed comes to being true to the picture.

I planted them early, perhaps way way to early because I was excited! At the begining of February and they can't go out until mid May. But, they are underlights and doing really really well. They don't seem leggy at all. I really recommend getting a shop light for anyone that is serious about growing from seed. A sunny window just does not really cut it.

Oh, and one tip for storing over winter if you only have a few, and don't have a dry cool place to keep them, is your fridge crisper, or get a large ziplock and some sort of storing medium, I really like wood shavings, the kind that they used for small animal bedding and it sold in petstores. A big bag is dirt cheap and works really really well!!

It's my first time growing Dahlia from seed this year too :)
I've never grown Dahlia before at all and can't wait to see what I will get!

I sowed on 4/5 (2) different seed both received in separate trades:
1. 'Bishop's 'Grandchildren' (saved seed from 'Bishop's Children' rec'd in fall 2007
2. 'Early Bird Mix' rec'd winter 2009 (extra commercial)

By 4/10 I had (4) 'Bishop's Grandchildren' seedlings and (5) 'Early Bird' with (1) more by 4/12. Not bad since I sowed only 8 seeds of each! Didn't even expect germination so quickly :)

Although both germinated at the same time 'Early Bird' growth rate is ahead of 'Bishop's' and are already going on 1st true leaves while the 'Bishop's haven't even started forming yet.
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Happy Gardening,

Vera