Heat a grill to high (450° to 550°) with a full chimney of coals if using charcoal. Brush corn with 1 tsp. oil. Grill corn and chiles, covered, turning occasionally, until corn is slightly toasted and chiles are lightly blackened, 6 to 10 minutes. Set corn aside and transfer chiles to a large bowl; cover to steam and loosen skins.
Whirl baguette in a food processor to make 2/3 cup coarse crumbs. Toast crumbs with remaining 2 1/2 tsp. oil in a medium frying pan over medium heat, stirring often, until golden and crisp, 5 minutes. Pour into a bowl and set aside. Add chorizo to pan, increase heat to medium-high, and cook, stirring, until brown and crumbly, 4 to 5 minutes. Transfer to a paper towel–lined plate.
Cut corn kernels from cob, then mix with chorizo, jack cheese, and queso fresco; set aside. Oil 2 large sheets of foil.
Peel skins from chiles. Make a 3- to 4-in. slit along length of each chile, starting at stem. Pull out seeds and some of base of stem to open up the cavity.
Set 2 chiles on each sheet of foil. Stuff chiles with cheese mixture and crimp sides of foil around them to create open packets. Set on a baking sheet.
Return grill to high (450° to 550°). Grill chile packets, covered, until cheese melts and chiles are hot (at least 160°) in middle of filling, about 5 minutes.
Smear some crema on each plate and top with a grilled chile. Sprinkle with chorizo bread crumbs and serve with salsa and cilantro.
MAKE AHEAD: Through step 4, up to 1 day, wrapped airtight and chilled; let stuffed chiles stand at room temperature 30 minutes before grilling, and cook 10 to 11 minutes.