Toss in the shrimp, and allow them to marinate for about 30 minutes.
To prepare the jicama slaw, place jicama, carrots, cabbage, and cilantro in a glass bowl and toss together until well combined.
Next, in a small bowl, mix together the pepper, salt and sugar, and sprinkle over the veggies tossing well to combine.
Prepare the marinade: In a small bowl combine oil, lime juice, rice wine vinegar, pepper, salt, and sugar. Mix well, then drizzle over the slaw, and use two spoons to completely coat.
To cook the shrimp, first remove them from the marinade and lightly pat dry. Heat a non stick skillet on medium and quickly sear the shrimp about 1-2 minutes on each side.
Place some jicama slaw on tortilla shell, and top with shrimp. Drizzle with sour cream if desired.