It would be a bad idea for you to represent yourself. I hear you say you can't afford an attorney but I would keep calling around. Attorneys fees and payment plans will vary widely. The DA isn't going to reduce a DWI unless they're concerned about winning at trial. They're not going to be concerned unless an experienced DWI attorney has reviewed the states evidence and pointed out weakness in their case.
Also if you can prove indigency the judge cannot deny you a court appointed attorney. If you make minimum wage and support several people you need to take proof of that with you to court--tax returns, bank statements, check stubs, etc.
Macy Jaggers's answer to a legal question on Avvo does not establish an attorney-client relationship. Please consult an attorney who practices criminal law in your jurisdiction for the most accurate legal advice.
It's very unlikely the DA will speak with you, even if you are not represented. As for the charge being reduced, there needs to be some compelling reason for doing so, and that's only going to happen after an attorney working on your behalf.
It's impossible to judge the merits of your case based on these facts. DWIs are technical and can be very complex. Refusal to provide a sample can be taken as evidence against you.
Bottom line: you need to hire an experienced DWI lawyer.
Answers to questions do not constitute legal advice, are for general purposes only and do not establish an attorney-client relationship.
Get an attorney. If you are truly indigent, the court will have to appoint you an attorney; that's the law! You will fair much better with legal representation than without, so get an attorney one way or another. As for the DA reducing the charge, that is unlikely unless the DA thinks they have a very weak case, and even more unlikely if you do not have an attorney. Some counties will offer Obstruction of a HWY/Intoxication if it is a first DWI to help keep the stigma of a DWI off your record, but I do not know about Harris County. The bottom line is this: you need an attorney, one way or another. Get one appointed, or go and hire one.
I practice criminal defense in Harris County every day. I have a number of current pending DWI's. We work every day to try to find arguments to get DWI cases dismissed. It is very difficult these days to get DA's to concede their DWI cases and dismiss them. These cases are almost never reduced in Harris County. Perhaps other counties offer that sort of resolution, but it is highly unlikely to happen in Harris County. The ONLY way to get a good result is to hire a defense lawyer to take a very detailed look at your case and find an argument that may ultimately persuade the DA or a jury to let you go.