They certainly have a presence in the country:
There are nine DEA Offices in the region located in Barbados, Curacao, Dominican Republic, Haiti, Jamaica, Guyana, Trinidad and Tobago, as well as Nassau, and Freeport, Bahamas.
and to quote the US Embassy for Haiti:
The DEA’s Port au Prince, Haiti Country Office assists the Government of Haiti develop and strengthen its counter-narcotics law enforcement program.
But do they carry out operations themselves? There's certainly precedent, they conducted an operation against the nephews of the Venezuelan President in 2015 and it sounds as though they identified themselves then:
CS-1 then left into the bathroom and the Haitian Brigade de Lutte contre le Trafic de Stupéfiants (BLTS) and DEA agents raided the restaurant after identifying themselves, apprehending the nephews
and the was a fairly dramatic-sounding raid (complete with helicopters) attempting to apprehend Guy Philippe in 2007:
Shortly after dawn on 16 July 2007, five helicopters, two planes and more than a dozen heavily armed DEA and Haitian anti-drug agents surrounded Philippe's home in the hills above Les Cayes, on Haiti's remote southern peninsula, to seize evidence of drug trafficking.
How often they carry out operations directly I don't know. The two examples above were the only two I could easily find and both pretty high-profile but whether that means they're exceptions to the norm because of their high-profile or whether the fact that they are high-profile is the reason they were news worthy.