Stucco often has wire mesh which as you recall is a Faraday cage. So maybe you need to call up Cisco or https://www.ubnt.com/ which does this and see how much this will be.
If you go cheap, it may work but with limitations.
I have a motel & cottage property, I offer free wifi to my guests. But after spending a fortune on 3 separate access points with large antenaes, my guests still cannot access it from within most rooms. outside seems to be ok. Moving around the property and having to reconnect to different access points is a total pain also.
Has anyone got a better solution???