laychris Professional riders have used indoor trainers for over a century. There is no shame in "riding the spinning bike". There are many reasons people make use of indoor spin bikes, schedules, weather, location...there is no shame.
There are many adults who never had the opportunity to learn to ride a bike when they were young; there is no shame.

A quick google search shows many bike shops (including some REI locations) offer adult beginner bicycling classes. I'm sure they are also offered at some YMCA's or community centers. All it takes is a patient, understanding instructor (or instructors).

If you don't feel comfortable or safe riding in traffic, there is no shame. I have been riding for over 50 years, and bike commuting seriously for 30, and there are streets and places I won't ride.

But there are plenty of parking lots and parks to develop your basic skills at your own pace without pressure. Depending on where you are there should be some trails where you don't have to worry about automobiles.

And when you are more comfortable with your riding, there should be many low-traffic streets or bike lanes where you can ride.

If you find you do have trouble riding and balancing a bicycle outside, you are not alone. That's why there adult tricycles, including the low-slung, two-wheels in front, recumbent types that are a whole lotta fun, and can be very fast, while being very stable. And again, absolutely no shame. When the late bicycling guru Sheldon Brown lost the ability to balance on two wheels, he continued on three with the same gusto.

And ignore the haters, they are not interested in helping you achieve your goals, and have nothing positive to add to your experience and enjoyment.

Good luck, have fun, and let us know how things are progressing.