The training varies from diocese to diocese, but all diaconal candidates have homiletic courses.
A few years ago, the number of deacons in our archdiocese (200) surpassed the number of priests. Priests are relying upon deacons more and more to assist in pastoral duties as the number of priests continues to decline.
Most of the larger parishes have deacons, and most of them preach on a regular basis (typically once a month).
As others have mentioned it’s very similar to priests: some deacons are extraordinary preachers, better than most priests. Others are noticeably weaker. Most are somewhere in the middle; just like the presbyterate.
There are deacons that parishioners seek out when it’s their weekend to preach, just as there are people who call parishes to find out when Fr. X is preaching, so as to avoid him.
Certainly you are likely to see them at wakes and such, as noted above.
I covered at greater length in another thread how [both] priests and deacons can improve their preaching.
Personally I spend considerable time preparing a homily, typically around 6-7 hours for an eight-minute homily. That’s a suggested ratio from one of the documents on preaching that all priests and deacons study.
Be thankful for all your blessings,
Deacon Christopher