Washingtonias are pretty easy from seed, but best germinated under something warm like grow lights. They probably need about 85-90F to germinate well.

I dont think they can grow 6 feet a year (especially if you are talking about 6 feet of trunk), but in a good climate (like the southwest) they do grow pretty quick, probably up to a foot of new trunk a year.
There are a few people on this site growing these palms in pretty cold zones (like in a zone 5), but I havent grown any all year long outside. Mine gets leaf damage at around 23F and completely defoliated at 18F, so it will need lots of protection if you want it outside all year long, but will quickly recover after the winter ends.

Good luck!

In z 8b where I am, they're planted all over the place. That said, it got down to 12 degrees in our recent cold snap and browned the leaves on most of them, including the one in my yard.

I'm sure most of them will come back, but they'll look lousy for the next few months.

W. filfera is definitely more cold hardy. I have a little guy about 6' tall that got some leaf burn, but still has quite a bit of green.

I'm also in zone 8 and some of them turned brown here too at 14F, although I'm sure they will survive.

W.filifera is more cold hardy but is less tolerant to moisture. Supposedly the hybrids (W.filibusta) have decent tolerance to both cold and moisture. I have some seeds so I will find out later this year.

I'm having a zone 8 or 9 winter our lows in ohio our about 30 and are highs are in the 40s. Which really isn't unusual for were I live. I live in a valley were trees protect from the wind but plants still get full sun.

Joseph, what has your coldest night got down to so far this winter?

About 5 or 10 and then it warmed up.

i think mexican fans are reliable to zone 8b. outside no protection. but with protection as low as zone 5, who knows maybe lower if you have excellent protection! ive heard of 3 ft. of trunk growth a year but in cali. but 6 ft. a year is not if at all common! am pretty sure the most it can get is maybe 4ft. but on a very good year which this might not happen very often. from seed there very easy! am actually growing some from seed & some washington filiferas. i have them in a ziplocked box like a plastic food or fruit box with 3/4 filled up with vermiculite & add about a few teaspoons of water & mix it but if its to moist let it dry alittle. it should be still fairly dry after u add the water. i have it in my closet with a heater in there. temp. 75-80*F. or u can just put them in a pot with potting soil with some heat & they should germinate fine but my best success is in a plastic box with vermiculite! usually i have atleast 90% success this way! washington filiferas germinate better with room temp. heat! goodluck!

Here's what they look like around here right now. These probably got down to about 16F.

Those robustas still look pretty good! They made it through some serious cold, and look like they will make a full recovery. One thing that is also a factor is they do look like they are in a pretty decent microclimate, which is very important.