Save and invest. That's what all of us had better be willing to do with our personal tax cuts, provided Congress passes the president's economic recovery program. Only then, we are told, would the president's program have a really solid chance to achieve the good things it promises; like pulling down the interest rate and inflation rate and boosting up productivity and national prosperity. But for any of these good things to happen, Congress must act, and then there has to follow a whole a lot of saving and investing. And that could be a big problem.

The homely truth is that a large plurality of the people in my precinct, including me, are functional investment illiterates. The same may be true in your precinct, too. No condescending snickers, please. We do not think that the Fortune 500 is a stock car race or that debentures are something a sitcom character keeps in a glass on a bedside table. But pork bellies and Krugerrands still draw a lot of blank stares.

Certainly our president has more than enough to do with his task of galvanizing popular and political support for his spending and tax cuts. But somebody had best convene an immediate crash course, for many of the rest of us, on the joy of investing or on everything you always wanted to know about certificates of deposit but were too embarrassed to ask.

The jargon and the shorthand of the investment crowd are enough to intimidate even the most cocky among us. Just look at the daily stock market reports in today's paper. Reading them compares with trying to decipher a fever thermometer in a closet. If the numbers are even legible, they are still confusing. About the only fun in reading the stock prices is the chance to see a purported grown-up get totally excited about a number like 9 5/8 unless it was my future brother-in-law's hat size.

Banks and lending institutions of all sizes and types frankly give me the hives. Nobody really believes that anyone, with the possible exception of David Rockefeller, has a friend at Chase Manhattan. Banks do not make very good chums or pals. Banks seem to care about earnings than yearnings. Most banks define being on good terms as your being on theirs.

Investment and economic language can be both confusing and off-putting. It doesn't take a grammar teacher to tell you that you don't simply "sell short": you sell somebody or something short, usually to your later regret. How about the supply-side economics of budget director David Stockman? Stockman, the point man for the administration, is a forceful and relentless advocate for turning more responsibility over to the private sector. His confidence must be more theoretical than personal because, since leaving divinity school a decade ago, he has not been off a public payroll.

But probably no single economic transaction can produce fear and misgivings in me like those generated by a certificate of deposit. CDs, I have concluded, are a permutation of the banks' Christmas Clubs. Remember the Christmas Club? You would put a few bucks in every payday and even if your hamster needed corrective shoes you could not get your own money out until the next December. You learned early that the money was not yours, it was theirs, the banks'.

Certificates of deposit, and most especially the commercials advertising them, terrify me. You've heard them where they tell you they'll pay you interest somewhere between the annual inflation rate and the prime interest rate if you leave your life savings with them for a decade or so. Well, every one of the commercials ends the same way. Some guy with a voice that makes Charlton Heston sound like a young Wayne Newton comes on and threatens: "Substantial penalty for early withdrawal." Make that: "SUBSTANTIAL PENALTY FOR EARLY WITHDRAWAL."

Now you tell me. What does that menacing advisory mean? Just exactly what is a substantial penalty? Do they repossess your dog or make you memorize the collectged speeches of Spiro Agnew?I don't know, but that guy scares me away from certificates of deposit. I won't have anything to do with any place offering CDs until they show me a clean bill of health from UNICEF.

It isn't as though we hadn't tried to understand these economic plans before. Four years ago, it was zero-based budgeting. That was going to eliminate deficits, balance the federal budget and put a half-nelson on inflation. Does anyone know what happened to zero-based budgeting? I don't believe it worked nearly as well as its supporters had hoped it would.

But right now I'm afraid that, without the president's active involvement in persuding large numbers of people that savings and investments are aboveboard and can be fun, his economic plan just won't work as it's supposed to.He could leave to someone else the job of explaining how a tax cut of $54 billion wil make up for a budget deficit of $45 billion -- and how the two of them will combine to lower inflation rates and cut interest rates. The Great Communicator's greatest challenge may very well be to teach us to invest without fear. If President Reagan succeeds, it might pay handsome dividends.