Well, A....it really all depends on a lot of things. For instance, will you be sending your child to a private school or will you want him to go to public school? Do you want to live close to your husband's job, your job or does that matter? If it does, where will you be working (he be working)? When you say affordable, what can you afford? Affordable to you may not be affordable to me.
I have been looking into various neighborhoods lately because I will be wanting to move within the next year and I've driven all over town and looked at lots of homes. I live in Little Forest Hills off of White Rock Lake and I love the homes and big trees...I even love the elementary school, but am not too fond of the middle school so I'm looking at Garland or Mesquite. Plano, Murphy, Allen, Frisco, Southlake, McKinney are too far north for me and my job is in Mesquite. I'm looking at Garland and Mesquite because you can get more home/property for your dollar than in the city of Dallas. I grew up in Lake Highlands which is not far from White Rock Lake and they have beautiful trees and are in the Richardson School District (which is good), but the homes are expensive. Old Lake Highlands (someone mentioned already) is a beautiful area and the homes are more affordable, but they are in the Dallas School District. Garland has something called "School Choice" which means that you can choose which Garland school you want your child to go to. I have heard that Forney is also a "small town" feeling city with decent schools.
Go to http://www.texasmls.com and you can browse homes for sale in various zip codes. Lake Highlands will be mostly 75231 and 75238, Old Lake Highlands/Lakewood/Little Forest Hills will be 75218 and 75214. Mesquite is 75150 and 75149 and some nice areas in Garland are 75043, 75041, 75042. Do a lot of research on the neighborhood though before you make an offer. There are some neighborhoods that look one way during the day and have a different look/feel at night.
Good Luck.