“I pray for you guys to get the papers, go to college,” Mrs. Teodoro said in English. Her daughter said she had arrived in the United States when she was 6 years old and had refused to return to Brazil with her mother in order to finish her undergraduate studies at the University of Massachusetts, Boston. Mrs. Teodoro was ordered deported after her husband’s asylum petition was denied.

The mother of another young immigrant, Carlos Padilla, 21, from Seattle, said she was “glad and sad at the same time: glad to be here next to him, sad because the fence is between us.” Mr. Padilla said his mother, Josefina Hernandez Madrigal, went to Mexico in 2008 to take care of ailing relatives and had not been able to obtain a visa to re-enter the United States.

A Border Patrol vehicle parked nearby, and an officer stayed to observe but did not intervene.

The Senate bill would offer significant gains for young immigrants like those in Nogales, but not for their parents. It includes a version of the Dream Act, the measure from which the young immigrants take their name, which would give them an expedited five-year pathway to American citizenship. Young immigrants like Ms. Teodoro and Mr. Padilla who had received deportation deferrals would have a faster application process for provisional status, the first step along that pathway.

The Senate bill would also allow some deportees to return to the United States, including children, spouses or parents of United States citizens or legal permanent residents, and youths who would have been eligible for the Dream Act. It does not have any measure allowing the return of deported parents of unauthorized immigrants. Several Republican senators have raised strong objections to any return of deportees, and that provision is considered one of the most endangered in the floor debate.