GENEVA — UN Secretary-General Javier Perez de Cuellar left Geneva yesterday hopeful but awaiting reaction to various proposals on the Middle East hostage crisis from Israel and the groups in Lebanon holding captives."I am really hopeful that we can reach an agreement," he told reporters before leaving Geneva for Lucerne, Switzerland for a few days' holiday. In Geneva the secretary-general had tried to cool optimism for an early release of remaining hostages. Asked if an agreement could be reached in days or weeks, he responded: "I don't know. Perhaps days or weeks, I don't know. It depends on how quickly I have reaction from both sides." "We now enter into some quiet diplomacy," Perez de Cuellar said after several days of highly public and intense contacts with Israeli, Iranian, and Western officials.