I am about to make a small (6'x3') raised bed. What would be the best tomato to plant this time of year? Haven't had any success so far with most of what I've tried to grow.
You did not say which USDA cold hardiness zone you live in. That's important, because in Arizona, there are a number of different ones, and it's important for raising plants, particularly vegetables.
However, it's not important now,because it's really too late in the year to plant tomatoes.
Tomatoes are tropical plants. Even if you live near Phoenix, which is warm even in the winter, you do get some days of frost which will kill your tomatoes.
Spend some time this fall and winter planning, finding out which USDA cold hardiness zone you live in, and which tomato plant varieties will do best.
There is a USDA cold hardiness zone map available on the National Arboretum's website (http://www.usna.usda.gov/Hardzone/ushzmap)
I would also contact my local county Cooperative Extension Agent, which is an adjunct of the University of Arizona. The info and service is free, and they have plenty of free literature on planting vegetables in your area.
Your county Cooperative Extension Service should be listed in your phone book under County Listings or you can go to this website and look for your county listing: http://ag.arizona.edu/extension
Here is a link that might be useful: Desert Gardens
I agree with Xeric about the time of year to plant tomatoes in Arizona. They are fussy here, but it can be done. Our window of production is short, as the plants don't like temperatures under 70, and above 90 to produce. Choose plants that ripen fast, such as "Early Girl". Roma's do well, and will continue to ripen as the heat returns. I have best luck with some heirloom, and international varieties. Look for plants that originated in the Middle East, Russia, E. Europe. They can be hard to find in Phoenix. One tomato that is good is "Pearson". You can find it at Baker Nursery in the spring. I plant in February, once the front has gone. You can do earlier with frost protection, such as "Wall of Water".
Meanwhile, many cool season crops are great through our winter. Radishes, carrots, Fava Beens, Chard, and lettuces are fun to grow.