Guayabera is a traditional men's shirt; it is quite popular in Cuba, the Caribbean, Southeast Asia, south of Spain and Portugal.
However, it is distinguished by its boxy cut and loose fit and soft collar. Also, you could see the vertical stripes of pleating or a nice embroidery on the front and the back of the shirt, with four patch pockets.
Although it comes with full (barrel cuffs)/ half sleeves, it's predominantly made of 100% linen and cotton; hence it's a perfect shirt for summer and also for your travels as well.
Interms of colours, it often comes in white and ivory; I would prefer to go with a lighter tone and paired with darker-tone trousers, most likely chinos, khakis and dark wash denim jeans.
Actually, the straight hem of this shirt is meant to be worn untucked, but if I wear it underneath the jacket, I prefer to tuck it in and make sure of a tailored fit; because I would rather feel uncomfortable.
Therefore, even in hot weather, I would like to layer my outfit with lighter fabrics, which I would say is quite a stylish statement and distinctiveness.
Hence, You could wear this shirt underneath an unstructured (which means no interlining and no shoulder padding) sport coat (cotton, linen, seersucker, hopsack, tropical wool) or perhaps with a summer suit as well.
Although if you would like to add a bit more casual touch, then a pair of espadrilles would be a nice choice. On the other hand, if you want to look a bit more dressy, a pair of brown penny loafers is quite a versatile choice for your look, I would say.
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