All Savers bide their time.

Are the All Savers certificates playing peek-a-boo? After all the publicity and the extra hours banks put in to sell the tax-exempt certificates, not much has been heard from them lately. Have they gone out of business?

No, but they're sort of lying low until around Halloween, when they'll be playing a game with a more appropriate title: trick-or-treat.

''Things have been pretty quiet lately,'' noted Victor Kramer, head of retail marketing at the Fidelity Funds, which acts as a servicing agent for two savings banks in Massachusetts. Fidelity, Oppenheimer, Merrill Lynch, and a number of other nonbank firms are providing this service, which permits a customer to buy an All Savers certificate over the phone, and have the paperwork, payments, and dividends processed for them.

But Mr. Kramer and others associated with All Savers do not expect too many phone calls before the end of the month.

''There's no reason for anybody to rush out and buy one of these things now, '' agrees James Kendall, spokesman for the United States League of Savings Associations, which represents much of the nation's savings-and-loan industry.

On Thursday, Oct. 29, Mr. Kendall explained, a new rate for the certificates will be announced. But this rate will not become effective until Monday, Nov. 2. , giving depositors two days to buy the certificates at the current 12.14 percent rate if the new rate turns out to be lower, something most experts see as a distinct possibility, considering the current softening in interest rates. There was a similar ''window'' at the end of September, when the rate dropped from 12.61 percent.

''We'll have this window at the end of every month,'' Kendall noted.

The space between these end-of-month windows is giving bankers time to assess the value of the certificates on their balance sheets while regulators tally up the impact on the US Treasury.

The first week All Savers cerificates were offered, advertising and media exposure helped them rack up more than $15 billion in sales. But much of that money went from passbook and other accounts, which did not help the banks much, because they were paying as much or more interest for the same money. At the same time, noted Treasury Secretary Donald Regan in testimony before the Senate Banking Committee last week, little if any money was coming from the bloated accounts of the money market mutual funds.

In fact, money market funds, which were supposed to have fallen back in terror at the All Savers certificates, continue to stand up well, in spite of - and probably because of - the publicity around All Savers.

In the first week the certificates were available, money funds scored one of their biggest gains ever, picking up some $2.5 billion in assets. The following week, according to money fund expert William E. Donoghue, the funds added $1.1 billion, to bring their total assets to $163.7 billion.

As a result, All Savers has not been the blessing Congress seemed to have in mind.

''The All Savers was clearly something the Congress intended as a rescue effort for the thrift industry,'' said Jonathan Gray, banking analyst with Sanford C. Berntein & Co., a New York securities firm.

But a lot of this potential benefit was diluted by two actions the Depository Institutions Deregulatory Committee (DIDC) took before the certificates were issued, Mr. Gray said, though the first has been at least temporarily suspended.

That was the increase in the interest on passbook savings accounts from 51/2 percent to 6 percent. This action, which was to have gone into effect Nov. 1, was deferred by the DIDC last week. Had it remained, Gray said, it would have cost the savings industry more money to maintain these accounts, even though they still do not offer enough interest to attract many new depositors, he said.

The second DIDC action - which has not been retracted - goes even further to nullify the effect of the All Savers certificates, Mr. Gray claims. This was the lifting of the 12 percent ceiling on another certificate, the one for ''small savers.'' Now, the thrifts must offer competitive rates on these 21/2-year notes - rates currently running over 16 percent. For many depositors, especially those who are not above the 30 percent federal tax bracket, these certificates make more sense than the All Savers.

As a result, he noted, while the furor over All Savers certificates has died down, ''Small Savers'' are growing two or three times as fast and the savings institutions are locked into paying the higher rates on each of them for 30 months instead of 12 to 14 months. The All Savers program is scheduled to go out of business at the end of next year. By then, Congress hoped, interest rates will be down and the troubles in the thrift industry will be ending.