Too old?!!! Rubbish!
We bought bikes (after ten, yes, TEN years of my cajoling my husband who steadfastly ignored me but eventually gave way and guess what? He absolutely loves it. and is probably even keener then me Grrr.) some eight years ago whilst in our sixties.
Cycling really is fun, with a capital F. As long as those other road users don't get you (and yes, I am one of those, too) and the chances are that they won't (think fear of flying v the number of miles flown etc.) you will become fitter and those endorphins will chase away any dose of the blues and you'll feel oh so happy at the end of a ride.
Those who don't cycle just don't understand the fun, which is OK, as there is more room on the road for us!
Please call your local council as they will very likely give you two lessons which are set at different levels. There is a 'beginners/never sat on a cycle'before' class which can be followed by a roadcraft lesson which will show how to cycle on the road.
Although I love it, I will admit to being a bit nervous of traffic but knowing I have the right training and doing the right thing (i.e. not driving up to a parked vehicle and then moving out round it, etc.) gives me confidence.
I also enjoy the off-road cycle paths and there are a surprising number of them around. Ex-Beeching railway lines are great too, and are 10 - 20-mile-ish long and give a great day out.
Is there a river or canal near you? Once you have your balance, cycling along these gives a very pleasant ride.
You will need to 'get your bottom in' but this comes with practice. One's posterior, no matter how well padded, um, er, 'naturally', takes a little training! You may have to stop every mile or two until your rear is 'trained'.
As has been said previously, never cycle without a high-visibility waistcoat (cheap as chips from many outlets) and a cycle helmet. Most sold in the UK have a kitemark and price is not indicative of quality. A £9.99 one should be perfectly fine.
If you take to cycling, a pair of padded trousers or shorts will help with comfort, as will a sprung gel-filled saddle.
I very much enjoy my cycle computer (a small gizmo which sits on the handlebars) as it computes my speed, distance etc. I just love it.
If you are on your own, 'Breeze' rides are recommended. I have done a few: these are for ladies only, led by a lady leader (well, I guess she's a lady - she was very well mannered...!). They vary in distance and difficulty and there are beginners rides, too. You will stop for coffee at a cafe and it is all very socialable
We had a cycling holiday abroad this year with our family and there were ten of us aged from five into our seventies and we had a great time. It is a very sociable thing to do.
Earlier this year, we needed a new car and when entering a car showroom, surprised the staff by asking for an immediate opening of the car boot. We would then produce our tape measure and measure the distance between the dropped rear seats and the rear door. If there was room for our cycles, we had a test drive. Everything else was secondary!
Our bikes (bought when I finally convinced 'imindoors' to give it a go) have brought much pleasure and I can really, REALLY recommend them.