When you lose interest in the zoo atmosphere of the Union and in the eat-up-and-get-out ambience of the Square's fast-food places, perhaps it's time to head for the more relaxed eating establishments in the Cambridge-Boston area.

For an interesting evening (and an escape from Cambridge), you might take the T into Boston and wander around town before choosing a restaurant. Chinatown and the North End (Boston's Italian district) are particularly good places to practice restaurant wanderlust on a low budget.

Chinatown, featuring fine food at generally low prices, is only a few blocks from the Essex subway station; if you want to avoid walking through the sleazy Combat Zone, however, you should take the subway only as far as the Washington St. station and then loop around the Zone to get to Chinatown.

The North End also boasts of low prices, and is easily accessible from either the Government Center or the Haymarket stops on the Green line.

In Cambridge, restaurants run the gamut in their fare, their atmosphere and, of course, their prices. As in Boston, the best strategy is to experiment--the reps of Harvard Square restaurants are often deceiving. (Some Cambridge folk, for example, still imagine that Ferdinand's offers a quiet, intimate atmosphere.)

There may come a time when you think a trip to a French restaurant is the only way to counter the effect of Union food on your morale and your palate. You begin to mull over all the familiar names--Ferdinand's, Chez Jean, and so on. Forget them. Go instead to Autre Chose, a relative newcomer to the Cambridge scene, located at 1105 Mass Ave.

Autre Chose features some of the finest French dishes in the Cambridge area; the restaurant also sports a surprise: the very reasonable prices. In addition, the atmosphere is relaxed but not noisy.

For more exotic European fare at moderate prices, you might try Grendel's Den, on Boylston St., and the Blue Parrot, Mt. Auburn St. And then, of course, there are the more specialized restaurants--Ahmed's (next to the Galeria) for French-Moroccan food, Brazilia (one of the better small eateries along Boylston St.), and the Hungry Persian (Eliot St.).

And if you don't feel like making the trip to Chinatown, you can choose from among several excellent Chinese restaurants lining Mass Ave. For a varied menu, Joyce Chen in Central Square is the place; for Szechuan, try the popular Hunan (Central Square) or Yenching (opposite Widener library). The brunch buffet at the Yenching is excellent and inexpensive. With all these excellent Chinese restaurants on our minds, we forgot all about the Hong Kong; you should, too.

In Mexican food, Cambridge offers two extremes in price and, we think, in quality. La Pinata (Eliot St.) features amazingly low-priced standard Mexican fare; unfortunately, the folks at La Pinata just went too far in trading off quality ingredients to get low prices. They may attract a lot of newcomers with those low prices, but we doubt many return. If you feel like checking it out anyway, just remember the words of someone we passed on the restaurant's stairs--"Stay away from the refrites, they could be repeatees." We didn't heed their advice. And we paid.

Casa Mexico(on Winthrop St. off Mt. Auburn) offers excellent food at fairly dear prices; although the prices are steep by Mexican restaurant standards, Casa Mexico has to be the clear choice over La Pinata.

Okay, now that you've already gone to Autre Chose and maybe your parents are in town, we can talk about Ferdinand's and Chez Jean. Ferdinand's is the more popular; it's a relaxed, rather noisy place with overpriced food. But so long as your parents are paying, it's great.

Chez Jean, on the other hand, is quiet--a popular place for The Big Date over the last 20-odd years, we hear. Just terrific food--maybe even worth the stiff prices.