Lygus bugs, (Lygus hesperus) are primarily an agricultural pest, affecting potato, strawberry and other crops. They're quite small (1/4 inch) with a yellow, black and brown pattern, and overwinters in weeds, especially mullein, and in duff. This article has pictures and more information Lygus Bugs on Potatoes https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9173.pdf
More common in our area at this time of the year are infestations of box elder bugs (Boisea rubrolineata), somewhat similar to lygus bugs but with distinctive red markings. They are also twice the size of lygus bugs at 1/2 inch. In the fall when leaves start to fall box elder bugs start looking for places to overwinter and are attracted to warm building walls on the south and west sides. They search for cracks and crevices on buildings, also in trees and tree bark. They are nuisance bugs, and don't bite or reproduce at this time. They have an offensive odor when crushed however. Their preferred host is box elder trees or other maples and their favorite food is box elder seed pods or the seed pods of other maples.
Insecticides are not very effective in controlling them. The best control is first to seal all cracks and crevices with silicone caulk. Inside vacuum them up and dispose of the bag. You can also use a wet-dry vacuum with water and detergent. Outside wash them off the walls or spray them with insecticidal soap, or laundry detergent diluted with water, but be careful around plants with laundry detergent. The insects have to be sprayed directly to have any effect. This article has pictures of box elder bugs and additional information on control, Box Elder Bugs http://extension.colostate.edu/topic-areas/insects/boxelder-bugs-5-522/.
You could also have marmorated stink bugs (Halymorpha halys). They have a distinctive shield shape and are very destructive in gardens. In the fall, like box elder bugs, stink bugs are looking for a safe, protected place to overwinter, and congregate on building walls where they look for cracks and crevices. You will see them on screens. Sealing surfaces with caulk is the best defense. These bugs are called stink bugs for a reason. Vacuum any that get into your condo with a wet-dry vac using soapy water. They can stink up your regular vacuum cleaner. Stink bugs are attracted to light; a pan of soapy water with a desk light above it can be used to collect them. This article has pictures and more information, IPM for Brown Marmorated Stink Bug http://www.stopbmsb.org/stopBMSB/assets/File/IPM-for-BMSB-Online.pdf.
If the bugs on your condo walls are not one of these three bugs, please send us pictures. We can help identify them and help you find ways to control them.