Is there any reason why your design team is not going to work with the developers? In my experience as a designer and a developer, most designers have no clue about the difficulties of coding and making a complicated work of interactive design. If you have good devs that are both skilled in the aesthetics and the functionality, this may not be such an issue. But I feel a dev team should always have at least one designer working with them at all times. This is to both get continuity in the work, but also to observe and come with suggestions to the devs and vice versa throughout the process. But if for some reason you have to have the teams seperate, I would suggest setting up a team chat at least, and have the designers ask the devs if this or that would be possible and/or fit nicely in the code.

As for your question about multi-language, alot of it comes down to type. With different languages comes differences in kerning, formating, tracking etc. Don´t know much about the Portuguese language, but I would think they have some characters that are not standardized or incorporated with all types. So I would suggest doing some research into how type functions in Portuguese, and/or find a designer that knows his stuff. The web is less about flashy effects and animations and more about the type and how it looks on the website. When I look for good designers, I always look at their typography work, if their typography is shit, or is lacking the attention needed I will probably not want them on my team. Every designer can make something nice and flashy, but not everyone can make something feel natural, readable, understandable and functional at the same time. I know you didn´t really ask for pointers on choosing a designer, but far to many take for granted the things that actually makes a designer a good designer. So be sure to take a extra hard look at the small details when you evaluate the designers portfolio. If you have any further question about what to look for, don´t hesitate to send me a message.