Tom,
Here are the requirements for naturalization. Since you're married to a Brazilian, the time your requirement to live continuously in Brazil before applying is reduced from four years to one. However, you must apply in Brazil, while living here, and after completing the minimum residence requirement:
CelpeBras is the acronym for "Certificado de Proficiência em LÃngua Portuguesa para Estrangeiros". I just took it last month.
It's usually offered twice a year, in Brazil and worldwide. 2019.1 was offered on May 28, and the Edital announcing it and setting the rules was issued by the Ministry of Education in the Diário Oficial on March 15. 2019.2 will probably be offered in or around October, so you should check for the Edital starting about two and a half months before.Â
You apply online. You should apply as soon as possible when applications open, because when all the vacancies in a test site are full, they may not open any more.
The application period for the May test was March 18-28. Payment was required by March 29, and proof of payment had to be emailed to the test site.  The charge within Brazil was R$180,00; I believe that the charge outside Brazil was $100.00 US.
The test is held at many locations in Brazil and worldwide, all the same day. In May, there was one testing location in the United Kingdom, at King's College London, with 20 openings.Â
As described by raqasu, the written test consists of four essay exercises: one about a video (played twice, test takers may take notes), one about an audio recording (also played twice), one about a current events article, like a feature article that might appear in a magazine, and one about an opinion piece, like a newspaper column. You have a half hour for the essay on the video, but may go back to it later if you don't complete it. You have three hours for the entire written test.
I took the test at the Federal University of Amazonas, one of the larger test sites. There were 180 seats available, and all appeared to be filled. We took the test in two auditoriums, with about 90 people in each, on clipboards that were provided -- auditorium seating, no desks. The video and audio were played over the auditorium sound system, and were pretty clear.
The oral exam can take place the same day, or the following day, depending on the number of test takers and evaluators. It consists of five minutes of conversation about the material you provide about yourself in a questionnaire you fill out on the application, and 15 minutes of discussion on three "provocative elements", visual aids that reference three contemporary topics, that you and the evaluator then discuss. The ones in my test were (1.) technology, what I have, what I like, technology purchases I've regretted, (2.) types of tourism, and (3.) "sebos" -- used book stores.
Passing requires a 2 out of 5, which is defined as "Intermediate:Â shows partial operational dominance of the Portuguese Language, showing capacity to understand and produce oral and written texts on limited subjects, in known contexts and everyday situations, presenting limitations and interference from the native language and/or other foreign languages in unfamiliar situations, not sufficient, however, to compromise communication."
The written and oral tests are graded separately, by different people. The composite grade is the LOWER of the two, so it's not possible to bootstrap a weak written test with a strong oral, or vice versa.
The Federal University of Rio Grande do Sul has a collection of tests from prior years at this site:Â
I found them extremely helpful for practice and for getting familiar with the logistics, like the expected length of each answer. They include the videos, audios, and "provocative elements" from the orals.
Any more questions, feel free to ask.
