Welcome to New Haven,
Some ideas:
Go to Trailblazers, they have postings there.
Try running on the trails at the bottom of East Rock.
You'll find warmer weather brings out more visible runners. Several local groups meet at Yale track weekdays for evening workouts.
Go to Hitekracing.com That is the website for local races, groups and message board.
Try "Sound Runner" running store in Branford, CT., not far from NH. Great group runs every weekend. Some young single runners, so if you are a single guy or girl, you might meet someone as well. If not, the group runs are all abilities.
Try "Woodbridge Running Co." on Landin St. in Woodbridge, CT. on the edge of New Haven. Go 2 + miles down Whalley Ave. They also have organized runs.
The city hosts the 20k national championship on Labor Day. It's a must for locals.
There is also a USATF/CT grand prix.
I hope this helps.
Welcome to New Haven, and good luck.