We have an AT@T wireless home phone, the only problem we have is, it will not
Let us send a fax. Think we will go back to a land line.

Looking at a HP 6700 Officejet Printer that says something about being WiFi.
Will this solve my problem and allow me to send a fax?

Probably not. Faxing is an analog process and requires an analog phone line. How frequently do you send faxes? Faxing is essentially an obsolete process clung to by a few diehards. Most people e-mail PDFs instead. If you have an occasional use for faxing, you might consider using efax.com rather than going back to an analog line.