Mercedes Calero, a Cuban refugee, and her infant son, Felipe,slept on a park bench for two nights before police took them to a shelter operated by Mother Teresa's Missionaries of Charity in downtown Miami.

Caridad Borrego, her partially disabled husband and their three small children are luckier than most of the 32,000 Cuban and Haitian refugees who lost their $119 monthly welfare checks in South Florida. They moved into a friend's garage.

And Julio Brizuela, a 61-year-old diesel mechanic who lost his job in a sugar mill last year, can no longer afford his $70 monthly rollaway bed in the hallway of a downtown building. He says he may go back to the 1972 Pontiac he lived in last winter.

The nationwide cancellation of welfare benefits to about 112,000 refugees who have been in the United States more than 18 months has hit Florida particularly hard.

About 38,000 of the 42,000 Cubans and Haitians whose welfare was canceled live in Florida, where there is no general state welfare program to pick up the slack.

Several other states can continue to provide medical and financial assistance to these refugees for another 18 months because federal reimbursement is available for their existing state welfare programs.

In Miami, where most of these refugees live, several hundred refugees already have moved into abandoned boats and houses or sleep on park benches, under expressways and in pup tents, according to local officials.

"Basically for these people, we are starting all over again," said Linda Berkowitz of the state's Department of Health and Rehabilitative Services.

Hundreds of Cubans and Haitians have been lining up at four centers in Miami since last Thursday to apply for emergency assistance for rent and food. The first day, the crush of 400 refugees at a Miami Beach center was chased away by police after a frightened official inside the building called for help.

Ten officers were sent to keep order in the 90-degree heat at another center in Little Haiti on Monday, and two mounted police paced their horses along a line that curled around a block at a center in Little Havana.

In most cases, refugees seeking immediate help were simply given appointments to return next week to apply for up to $100 in one-time rental assistance and a $20 bag of groceries under a $5 million federal emergency grant.

"We have to take an application to make sure they're eligible," Berkowitz said.

About 11,000 of the 32,000 Dade County refugees whose aid stopped will be eligible for the limited assistance, she said. Others may qualify for food stamps and benefits under Aid to Families With Dependent Children. But many who showed up had no idea where to turn.

Florida is seeking $34.9 million in federal impact aid to replace the money promised by the Carter administration for 36 months, but shortened under Reagan to 18. The state also has sued the federal government for $10 million in refugee costs since the federal aid stopped April 1. (Florida law required that recipients be given two months notice before aid could be cut off.) Florida rejected a $31 million compromise offer of impact aid by Richard Schweiker, secretary for the U.S. Department of Health and Human Services, in exchange for dropping its law suit.

"That is not a very good offer," said David Pingree, Florida's secretary of Health and Rehabilitative Services.

The $5 million in emergency aid to Dade County will provide rental assistance and groceries, establish a job-training program for about 4,000 refugees at $1.75 an hour and continue refugee medical care at county-owned Jackson Memorial Hospital.

Already the hospital holds $7.4 million in unpaid bills which it contends the federal government owes for the care of indigent refugees. Governments and private agencies in Florida argue that refugee aid is a federal, not a state, responsibility.

If the federal money does not come--and quickly--local officials fear an increase in crime of the kind that occurred following the Mariel boatlift. "If you cut off the people and put them in the streets, who takes up the slack?" said Michael Pszyk Jr. of Church World Service.