Combine the grapefruit segments, jicama, red onion, cilantro, lime juice and 1 tablespoon olive oil in a medium bowl; season with salt and pepper and toss. Set aside.
Brush a grill pan with olive oil and heat over medium-high heat. Working in batches, grill the tortillas until toasted, 1 to 2 minutes per side. Wrap in foil to keep warm; set aside.
Meanwhile, combine the grapefruit juice, agave, chipotle and adobo sauce and cumin in a small saucepan over medium-high heat. Cook, stirring occasionally, until slightly thickened, 5 minutes.
Toss the shrimp with the remaining 1 tablespoon olive oil and season with salt and pepper. Brush the grill pan with more olive oil. Grill the shrimp over medium-high heat, brushing with some of the grapefruit sauce, until lightly charred, about 1 minute per side. Continue to cook, flipping and brushing with the remaining sauce, until charred and cooked through, about 2 more minutes. Season with salt. Divide among the tortillas. Serve with the grapefruit salad and lime wedges.