I once handled a very similar case for an immigrant with a Canadian arrest warrant. What we did back then is
1. I found an excellent attorney in Canada to handle the criminal case. You need to try to get a lawyer there and have him/her start trying to negotiate a plea agreement with the prosecutor. Usually, if you go there, you will be immediately arrested and will have to remain in prison until someone posts a bond. Moreover, you will not be able to leave the city (usually this is your bond condition). Thus, hiring a local lawyer there who can at least negotiate them not arresting you sounds like a good idea. I the case with Canada I mentioned, the canadian lawyer managed to get the criminal case dismissed without my client ever having to go there.
2. Now, regarding your first question about the arrest. In general, my answer is no. However, you did not provide any details about your immigration status now or prior to the departure from the country. Did you ever accumulate illegal overstay? Did you have any problems with immigration before? Do you have a green card? Overall, if your immigration papers are in perfect shape now and you never had any immigration probolems before and you have legal grounds to enter US, you sould be fine. You see, an outstanding arrest warrant is not yet a conviction. There is such thing as presumption of innocence until you are proven guilty. Thus, first you need to be convicted of a crime and then this might have serious implications on your immigration status. Consequently, you really need to fight this criminal case and hopefully get it dismissed. Ans then you should be just fine.

If you are a US citizen, immigration authorities do not have any reason to arrest you. Whether federal authorities at the border will have a record showing your warrant status, and arrest you under the warrant, is another question. As I am not a Florida attorney, I can't tell you what Florida's extradition policy is on a felony warrant for Washington State. Typically, the only way to quash (or remove) a warrant in the State of Washington is by going to court and appearing.

Although an attorney might attempt to have a warrant quashed without you being present, in my experience it is unlikely that the court will agree to do so. You should contact a Washington lawyer who handles criminal cases regularly in the county where you are being charged. The lawyer can help you figure out what kind of bail is likely to be set, can speak with the prosecutor on your behalf, and can protect you from providing potentially incriminating information to the authorities. It is usually wise to avoid talking to any police or authorities about the facts of the incident without an attorney present. If you hire an attorney in connection with the matter, in Washington State this will give you a layer of protection so that when you tell them to talk to your attorney, not to you, law enforcement would be obligated to stop trying to get you to give them more information. Even innocent people can provide information that may may be used against them to try to show they are guilty.

If you arrange to make bail in advance, once you appear in court, you may be able to avoid being detained any further. If you are told by a Florida attorney that it is safe to fly into Florida without risking arrest, it might make sense to do that and then come to Washington. If there is concern that you will be arrested and extradited, extradition can be cumbersome and result in you having to spend many days in jail unnecesarily. If it is likely you would be arrested and then extradited from your planned state of entry to the US, I would recommend flying straight into Washington State from outside the US. You should be able to get a Mexico/SeaTac connection at least. This way, if you are taken into custody, the process of getting you to the jurisdiction where you are being charged will be quicker and streamlined as you will already be in Washington State. It's probably better to fly in on a Sunday night Monday or Tuesday so that you won't get stuck in jail over the weekend for no reason.

Again, if you contact a skilled attorney who works in the county where you are being charged, the attorney should be able to find a way to expedite things, at the very least. A skilled attorney may also be able to get you permission to travel while the case is pending but the decision would ultimately be in the hands of the judge. If you voluntarily come to Washington and turn yourself in, the chance of having more lenient release conditions are better.