Obviously the popular and safe bet is New Dawn, however bloom varies for some as far as repeat. It is definitely most vigorous though and easily gets to 20ft once it matures. Mine is in it's 1st year and it is every bit of 9ft right now and still going. New Dawn is mostly a white, with a pink tinge to it. From a distance it tends to look mostly white though or faintly pink. Many people claim New Dawn doesn't have much of a fragrance, but mine definitely has one, especially when there are many blooms on at one time. It's certainly not strong, but what the blooms lack in strength, they make up for in numbers. Where exactly are you training it on your porch? Are you putting up white lattice, along the fence, etc? I am SURE there are people with many more suggestions and even better ones from their own experiences. Here is a link that might be useful: HMF New Dawn

Vedia Eidelman - Bouganvillea is tropical, and is hardy in zones 10 and 11. It can be grown in zone 9 if in a protected location. You can grow it in a pot, outdoors, but if you have a greenhouse where it can have a longer period of warmth, it would provide you with more growth. Obviously you would need to heat the greenhouse, or at the least, bring the container inside when temps start getting in the 30's. Growing it outside, and leaving it, in your zone, will simply be treating it as an annual. It will not survive.

I would say that Sabal Palmetto is the best one out of those for you to try but I also recommend Butia Odorata, Capitata, and Yatay. I'm in zone 8b Montgomery, AL and these are very tolerant of cold. We got down to 13F a couple of years ago and almost all got through it with no damage whatsoever. However if you're willing to protect a palm extensively it's worth trying almost any of them. Right now I have a Phoenix Roebelini, Queen, Cat palm, Majesty palm, and two Mule palms planted in my backyard. Most I planted early this spring but the Phoenix Roebelinii survived the winter in a heated, portable greenhouse. Our minimum low this past winter was 24F and when I took the greenhouse down in March there was only a tiny amount of cold damage on the newest fronds. Since then it's recovered fully.

Park Seed is a company I would recommend. Full afternoon sun is different than full morning sun, so if it is shade in the am and full sun in the PM in hot dry conditions, might as well be full sun. Are you just thinking planters or garden too? Coreopsis is an easy to grow from seed plant but it is perennial and like all perennials, starts out a bit slow but really takes off later on. Can't beat petunias for full sun, they are easy to grow from seed. So actually are old fashioned geraniums. Another perennial that would be perfect for you would be gaillardia, which goes by the common name "Prairie Blanket." Good both in the ground and containers. Marigolds easy from seed. Those are all kind of common in the big box stores except for the gaillardia and corepsis. The thing that I do with the common big box annuals when I'm growing from seed, is get a color or variation that is not commonly found. Another plant is alyssum. I've grown peach and yellowish ones, but I actually prefer the purple ones for their scent. Carnation and lavender, also easy to grow from seed. Perennials but look good the first year. Anything in the mint family, which includes bee balm, monarda, salvias and oregano, etc. Many types of verbenas, both dwarf and tall. Also same with snapdragons. Most have a dry spell midsummer, but some more everblooming than others. Then there are the many wonderful members of the sunflower family . . . morning glories easy to grow from seed . . . echinacea but watch out if you have deer and bunnies, they love it. Little begonias, angel wings and impatiens all easy or relatively easy to grow for shade. Lobelia is a fave of mine for shade, but in needs serious shade, any variety. Ajuga as a flowering groundcover for shade . . . ice plant. Honestly if you peruse some of the good seed catalogs you will be astounded. Yarrow, pansies if you keep them cut back bloom all summer . . . it would be easier for me to tell you what doesn't work--milkweed. It's fine to sow in the garden, but very hard to start ahead of time. Sorry I can't recommend other seed companies, but I buy from ones mostly in my zone, which is moist and northern. Harris, Stokes, Johnny's. Better to support smaller regional seed companies, IMHO. When we bought for plant sales and landscaping at the greenhouse, we bought in bulk, which is why I am not as familiar with good small seed companies. I always found something fun at Park, and they are great for customer service and philanthropy. Home base is S. Carolina? maybe north but I think south. But they have growers all over the country.