It is particularly foreigners who gape at the phallic symbolism of the Hieronymus Bosch version of the "Garden of Delights" and the mystical elongations of Greco's Byzantine "Adoration of the Shepherds." But many of the gapers are absent this year.

The number of visitors to Madrid's Prado museum last month was 16 percent lower than in the same month last year. The July tourist census released by the Spanish Tourist Board shows that 6.7 million came in July last year and 5.6 million this July.

On the face of it, this should make life more pleasant for everyone here, with the exception of government officials who are wondering how to manage next year's deficit. But life has not become more pleasant since the rising prices that have kept the tourists away - hotel rates are up an average of 38 percent - also plague everyone. Prices, along with a rash of muggers and a dearth of servants, are the constant moan of middle-class Spaniards.

Two old men were grumbling recently about the price of melons, now more than 33 cents a pound.

"When I was young in pueblo they used to give them away," grumbled the first. "And when they didn't, we used to steal them," agreed the second.

Never mind the tourist whose restricted budget does not include a flight to Malaga this year. Pity the Spaniard who has to pay a dollar for a glass of lemon juice to quench his thirst when the heat never drops below about 88 degrees Fahrenheit, even at night.

THE BLINDS have been pulled down on bars, shops and restaurants, and notices proclaim that proprietors are on vacation for all of August. The few residents still in town make it a point of honor to know half a dozen convival spots that remain open and to share the information with their friends.

The air-conditioned bar was packed. It was a hallowed haunt of Madrid's "Rodriguez." The name is the Spanish equivalent of Jones and is applied to anyone who remains in Madrid, having dispatched his wife, children, mother-in-law and maid - if they still have one - to an overpriced and undersized apartment by the coast. He becomes a "Rodriquez," a lone wolf, sweating for a few hours in his office and then footloose on the town.

"Rodriguez" is a part of Spanish summer folklore. He sets forth on an evening, holding in his stomach, having carefully combed his thinning hair and liberally made use of the after shave - a 20th-century, middle-aged Don Juan ready to grasp all the world has to offer with both hands. The next day, in the office, he tells great tales to his colleagues, but they too are "Rodriguez" and will top any real or imagined conquest this hero made with their own more fantastic achievements.

IN HIS ENDLESS pursuit of a youth he never really lived, "Rodriguez" misses the best late-night entertainment in town in the charming Plaza de Santa Ana, in the center of old Madrid.One side of the square is taken up by the modernist architecture of the now slightly shabby Hotel Victoria. The great matador Manolete used to stay there until he was killed by a Miura bull in 1947, and now the place is booked solid by charter flight operators.

Another side is taken up by the Doric columnsof the Spanish National Theater, which partially burned down a few year's back and has yet to be reopened. On one corner stands the Alemana beer hall, the best bar in Madrid. It is, inevitably, closed for vacation. At the edge of the plaza there is a statue of Pedro Calderon de la Barca, the most glorious of the Golden Age Dramatists.

As if to make up for the affronts suffered by the Hotel Victoria and the National Theater, not to mention the closure of the Alemana, the city council has sponsored an open-air production in the plaza of one of Calderon's most delightful plays, "La Dana Duende" (The Ghostly Lady). It is great Golden Age stuff, a baroque theme of honor, lyrical passages of courtly love, an element of mystery and a good dose of bawdy slapstick fun. The cast is young, professional and enthusiastic, the prices are cutrate.

Perhaps the tourist board should tell something different, something far from the maddening, crowded beaches where nonstop loudspeakers announce the discovery of lost children. They should sell Madrid during the vacation season, where it is peaceful in the park in the cool of the early morning, where one can be amused by the "Rodriguez" in the evenings, and where one can spend time with El Greco in uncluttered galleries at midday and with Calderon, in a secluded plaza, late at night.

But then everyone would come and spoil it.