This may sound like a good or bad idea based on an individual's unique situation surrounding the arrest and charges strength of evidence in the case belief or disbelief in one's own guilt. The potential consequences of the reduced charge vs. the potential for a guilty conviction based on the greater original offense whether the reduced charge will satisfy objective conditions such as: keeping a job, driver's license, child custody, visa/immigration status, freedom from custody, auto insurance, etc.
Mainly, the real decision lies on just what the San Diego District Attorneys Office is offering you;
Are they offering a wet reckless charge instead of a first offense DUI with a high BAC enhancement because you blew a .21% breath test result? The decision will vary from case to case, as a wet reckless charge will still appear as a high risk alcohol related incident to your auto insurance carrier. Not only that, but if you receive another DUI charge within a ten year period from the date you were initially arrested on the charge that was reduced to a wet reckless, the wet reckless will become a prior-able offense in court, elevating the next DUI to a second offense.
A good DUI attorney who is familiar with the details surrounding your arrest can help you determine whether the evidence against will hold up in court. It could be that the breathalyzer equipment used was not properly maintained, or a phlebotomist was not properly licensed, or even a break in the chain of custody of evidence that could substantiate a complete dismissal of the case when motioned by the attorney in lieu some facts, if they apply.
Be sure to consult with an attorney who knows California DUI law inside and out, and is certified in the equipment and testing methods used in your particular case.