Razorrock
I've lived and biked (and bike commuted) here in Colorado Springs for 29 years. I grew up in Chicago, so I always take precautions against bike and car theft, but Colorado Springs isn't Chicago, or even Denver in terms of bike theft...not yet. But still, I wouldn't leave my bikes locked up outside overnight.
Downtown is small and quaint for a city this size, and there are many improperly locked bikes that make easier targets than properly locked bikes. In most parts of town I feel comfortable locking my bike during the day for an hour or two with a thick cable chain through the wheels and frames. I take my bike computer and water bottle with me. Anything that can easily be removed and walked away with by the indigent. If your seats are quick release, make sure you lock those, too.
Central and North are pretty safe. South, near-east and south-east are lower-income and tend to have higher crime as a result, but still, not anything like even medium-sized cities.
My advice is if you are thinking about upgrading your lock...do it. You probably won't need it, but it will bring you peace of mind and help you enjoy your vacation.
By the way, this is goat-head thorn country. You'll need puncture-resistant tires, tire-sealant or tire-liners. I've been running tire-liners for almost 20-years and they made a huge difference! As a daily rider, before tire liners I would flat about twice a month. Since tire protection, maybe 1-2 times a year.
Also, Colorado Springs is about 6500' up (7250' on the north end), Estes Park is 7500'. You may find yourself a little short of breath the first few days. And COVER UP! You'll sunburn faster than you realize (Don't forget your neck.)
I don't know where you are staying, but one other bike option is to leave your bikes in your hotel room and use the Pike Ride bike share bikes to head downtown or over to Old Colorado City.
https://www.pikeride.org/
(They have a map of their area of operation.) They're not everybody's style of riding, but they're electric assist, which you may appreciate with the hills here and at our altitude.
Colorado Springs is a fantastic bike town...I'm sure you will enjoy it!
https://www.bikesprings.org/Ride-Resources