Many homes in Rancho Santa Fe suffer from poor cellular coverage. While the RSF Association is working on a plan to improve wireless coverage, it isn't expected to bear fruit until the 2018-2019 timeframe at the earliest.
However, starting in 2016, the major carriers and smartphones started supporting something called Wi-Fi Calling. The basic idea is that when your phone senses poor cellular coverage, but has a strong Wi-Fi connection to the Internet, it makes and receives calls over the Internet, bypassing the weak cellular network.
The major carriers (at least Verizon, AT&T, and Sprint) and recent Smartphones (iPhone 5s and above, relatively recent Android phones) support Wi-Fi calling. Depending on your carrier, you may have to call them to make sure it is enabled on your account (usually this is free).
Turning on the feature is easy - for instance on an iPhone, go into Settings, scroll down for the Phone setting, and then you'll see a Wi-Fi Calling setting. When turning this on, you'll need to set your Emergency Contact Location in case you make 911 calls while being on Wi-Fi. Consult a google search/carrier instructions on how to turn this on for Android or other Smartphones.
When Wi-Fi calling is enabled, your phone will switch between the cellular network and Wi-Fi seamlessly without you having to worry about it. It will even do soft hand off from the cellular network to your home Wi-Fi, for instance when you arrive home on a call in your car, and vice versa.
The cellular carriers used to (and maybe still do) sell an approx. $250 box that would act as a micro cellular site that also uses the Internet to carry calls. But these microcell devices never worked very well since their coverage area was so small - they would work only in a few rooms. Assuming you have good Wi-Fi coverage in your home, you can have crystal clear cell calls anywhere using Wi-Fi Calling instead.
This immediately brings up another point however. How good is your Wi-Fi Internet anyways?
First, the good news is that even if you have a crappy 2 Mbps DSL Internet connection, Wi-Fi calling should work fine since voice over Internet doesn't use much bandwidth at all (like 0.04 Mbps).
The bigger issue is that people sometimes struggle building a robust Wi-Fi network in their homes. Click here for some recommendations on building a robust WiFi network.