I am a 46 year old male taking care of my 86 year old mother-in-law. My wife works long hours and I am having to do so many things. I thinks most days I just need someone to talk to doing the day. On average my wife is gone from the house from 7:30 am till between 6:30 to 8 pm. Its so much harder than I thought it would be. We have been living here for 18 months now.
By the time your wife comes home at night you are both so tired from very long days I doubt that you have a lot of high-quality communication time. Sigh.
Does MIL require constant supervision? If she can be left alone for a while you will have more options, but assuming she can't be alone, one of the really great options is the one vegas lady already mentioned -- adult day care (usually called adult day health programs). This has to be set up on a schedule (rather than drop in) but the days and hours can be very flexible. My husband went 9 to 3, 3 days a week. Some people there went every day, 7:30 to 5, while their caregiver worked. Others went just once a week. A simple breakfast and a hot noon meal were available. They also had services such as helping with a shower and trimming toenails. If MIL is on (or is eligible for) Medicaid, in many states the day care service is paid for through the waiver program.
OR ... find a volunteer program or hire a companion (with MIL's funds) to come in for a few hours each day. Go meet your wife for lunch. Golf. Join a daytime bowling league. Do something that gets you out and talking to other people.
Get on AgingCare daily. Answer other people's posts. Post your own concerns. This is a meaningful kind of "talking to adults" every day.
I used to get up "lunch meetings" with a friend in another state. We blocked our calendars, ate our lunch, and talked on the phone. Sometimes I had to go and do something for my husband, but usually we had the scheduled time to ourselves. Do you have friends who are available for a phone date during the day?
Join a caregivers' support group. If possible, find one that meets during the day and arrange for care for MIL. If necessary, though, do it in the evening when Wife can be with her mother. I hate to reduce the limited time you two have together, but a support group is worth it.
This is hard. You are isolated, making it harder. Your wife may appreciate what you are doing to the nth degree (let's hope so) but even she may not truly understand what you are going through.
It may be work to arrange it, but get some time off from the caregiving, and break out of the isolation. You are worth it!