1. Combine first 3 ingredients in a small jar, and set aside.
2. Peel and section 2 tangelos; set aside. Squeeze juice from remaining 3 tan-gelos to measure 1/2 cup juice. Combine juice and honey in a small saucepan, stirring well. Bring juice mixture to a boil; cook, uncovered, until reduced to 1/3 cup, stirring occasionally. Remove from heat, and cool completely. Add juice mixture to mustard mixture in jar; cover tightly, and shake vigorously.
3. Combine watercress, arugula, and endive in a bowl; add mustard mixture, and toss gently. Place watercress mixture evenly on individual salad plates; top with tangelo sections and strawberry slices.