President Reagan's much publicized meeting with two Arab foreign ministers caused a mild whiff of optimism to drift through the sultry Washington summer.
But interviews with several Arab diplomats and American specialists on the Middle East on the day after the July 20 meeting indicated that so far results are modest indeed. There are still numerous questions to be answered before the Lebanon crisis can be resolved.
For those in the US, Israeli, and Lebanese governments who want to look on the positive side, however, there are:
* Indications from Arabs who represent a wide diversity - Saudi Arabia and Syria - that Arab nations will find places for the fighters and leaders of the Palestine Liberation Organization if and when the PLO leaves Beirut.
* Indications that the PLO is indeed willing to leave.
* Signs from Syria, which seemed at one point to oppose taking in any of the PLO men now in Beirut, that while it hesitates to take in fighters, it will accept the PLO's Beirut bureaucracy to add to those PLO bureaucrats already in Damascus.
For the PLO and its Arab backers, the positive sign is, in the words of Clovis Maksoud, the Arab League representative here, a ''greater sensitivity'' within the Reagan administration to ''the legitimacy of our rights than there was before.''
Yes, say American officials, there is a greater sensitivity on the part of Secretary of State George P. Shultz to the depth of Arab feeling over the Palestinian issue than there was on the part of his predecessor, Alexander M. Haig Jr.
But this does not mean, they say, the Americans are in a position to move as far as the Arabs, and the PLO in particular, want them to move. They fear that the Arabs, while looking for political gains, may be losing sight of an Israeli time bomb ticking outside West Beirut.
As State Department officials see it, all the signals now coming from the PLO , which seem to point toward an acceptance of Israel, lack clarity and authority. If the US responded, one official said, it would result in ''the PLO being on board and Israel off.''
''We see a lot of feinting and political movement from the PLO - a lot of dust in the air,'' the official said. ''So far, it comes to nothing.''
The official said the Arabs were looking for a statement from the US ''that it is ready to go to the mat with Israel to get the Palestinian problem solved.''
He said that the closest the US got to that point in the past was President Carter's short-lived advocacy of a Palestinian ''homeland'' in 1977. Subsequent signals led the US and the PLO close to direct negotiations. But, according to this official, Yasser Arafat, the PLO chairman, could not, at the last minute, bring his faction-ridden organization together in support of a statement accepting Israel's right to exist within secure, defensible borders.
''We're not going to go down that road again,'' the official said.