Need more info to give recommendation...
1) What are your salary expectations (ball-park)?
2) What kind of research & engineering do you do? I ask, because there are regions that have higher concentrations in each arena. For example, I live in an area where there dozens of Fortune 500 companies. One area has a great deal of biomedical research firms (MedImmune, Genome Research, Bayer, Physer, National Institute of Health, etc). Another area has a large number of IT companies (Nextel, Oracle, NCR, Intelix, AOL, etc).
3) How concerned are you about climate?
4) Do you have kids that attend school?
My knee jerk response would be to consider the Research Triangle Park in North Carolina. Areas near Raleigh have been rating in the top five places to live in the U.S. The cost of living is low, but the crime rate is low (may not be good for your wife). Income is average to below average, but really nice place to live (laid back). Acerage is available (away from coast).
If you are an aircraft research engineer, then Texas would be a good place... Dallas-Ft. Worth area or south towards Austin. Bell is based there. Brantly is based there. There are more heliports in Texas than there are airports (almost). Very hot there!