There is no real answer to your question because each Grand Jury presentation depends upon how many witnesses are to be presented and how long the Jury wishes to deliberate. Of course, if the case is relatively simple and all witnesses have already been before the Grand Jury, then it is not likely to take that long to make a decision since the level of proof is so low for an Indictment. In that situation, you are likely to hear next week or shortly thereafter.
I am not familiar with the procedure in Florida, but a federal grand jury in Philadelphia sits once a week for 18 months at a time. They can hear evidence for multiple cases or one large one, depending on the circumstances, and their time can be extended if necessary. Without knowing more about the nature of the investigation, it is impossible to predict how long the grand jury will take before deciding whether or not to return an indictment against you.
(Please note that this answer does not constitute legal advice nor does it establish an attorney-client relationship.)
This is posted in Federal Crime so I ma assuming it is a federal question. The short answer is that federal grand juries seldom take very much time to deliberate. They are presented all the evidence by the AUSAs, told by the AUSAs what the law is and then are given a pre-typed Indictment by the AUSAs.
The real questions are what is the grand jury doing and what was your fiancee's involvement? If this is an investgaatve pahse, then the AUSA may be calling reluctant witnesses to bring in documents (and, on occasion, actually testify) rpior to a decision to actually present the case for indictment. If so, then there is no way to determine when, if ever, the case will actually be presented. If, on the other hand, this is an actual presentment (where the indictment has been typed up and there is an organized presentation and request that the grand jury return the indictment), it is usually pretty streamlined. In that case, unless it is some sort fo extended organized crime case, or the like, the witnesses could be presented in a day or a few days with the return of the indictment pretty quickly after the close fo evidence.
Now, if your fiancee was simply an innocent witness, he should be able to obtain some information format the Agent who is making the arrangements for him to testify. He can also consult his own lawyer. If he is involved somehow and could be considered a subject of the investigation, he definitely should have had his own lawyer. If this is federal and he is a target, he should not have been called before the grand jury. Obviously, if he is a target, he should have the advice of his own lawyer immediately.
If this is a state grand jury, then you should consult a lawyer who practices in that state. Either way, this is not legal advice and, if you or he need advice, contact a lawyer and bring all of your information to her or him. Best of luck!