I was recently pulled over for suspected DUI and they did not read me my Miranda rights or observe me for 15 minutes.

No. But if you were interrogated while in custody, you can move to suppress statements.

My boyfriend and I were arrested for theft

Only if you were interrogated while in custody.

Contesting a speeding ticket?

No. You can plead not guilty.

What is the probability of a bond being reduced at a preliminary hearing for someone whose bond is over 400,000$?

Possible, but difficult to accurately assess without knowing defendant's background and strength of evidence.

What is the length of time for case to go to to grand jury?

Depends on state. In New York and many states, the time is 6 months from date matter was waived to grand jury or date of preliminary hearing,...

Go court tomorrow and was ordered to do community service 120 hours but do to my lupus I haven't been able to complete.

If you explain to Judge, you might be able to get more time.

If you don't return for court, yes.

Probably not. Taking information is a normal investigative procedure, and it's likely the police are more concerned about the parlor than its...

What should I do if arrested for a law already ruled unconstitutional and plead no contest to charges and sentence disposed of.

You can file a motion seeking to vacate (take back) the plea.

Do I need a criminal defense lawyer?

Yes.