In the second inning, Hidalgo's two-run homer off the left field foul pole gave Texas a 2-0 lead. Hidalgo, a streaky hitter during seven seasons in the National League, added a solo drive in the seventh to make it 4-2.
"I'm feeling more comfortable," Hidalgo said. "I've got it in my mind to stay aggressive, and whatever happens, happens."
Hidalgo, who has three homers in his last three games, raised his average to .216.
"You've seen him in the last week, he's been ripping the cover off the ball," teammate Rod Barajas said. "If he keeps hitting like that, he's going to help us."
Barajas and Drese were involved in a confrontation in the Texas dugout in the middle of the sixth inning, apparently over pitch selection. Teammates and manager Buck Showalter separated the pair, who were on the ground, and Barajas and Drese later shook hands when Drese was pulled from the game after the seventh.
After the game, Showalter acknowledged the episode but downplayed it. Barajas and Drese refused to comment.
Drese (4-4), who had lost three of his previous four decisions, allowed two runs and seven hits in seven innings.
"It was good for him not to be firing on all cylinders and have success," Showalter said.
Francisco Cordero got three outs for his major league-leading 15th save in 17 chances, helping the Rangers (25-20) move five games over .500 for the first time this season.
Terrence Long hit a one-out single, took third on Ruben Gotay's
double and scored when second baseman Alfonso Soriano bobbled the relay throw for an error. With Gotay on second, Cordero struck out Angel Berroa and then ended the game by throwing a called third strike past David DeJesus.
Hernandez gave up three runs and five hits in six innings for Kansas City, which dropped to 6-15 on the road.
Mench led off the second with a single, and Hidalgo connected on a 0-2 pitch for the 2-0 lead. Hernandez settled in to retire 13 straight from the second through the sixth until Soriano's single in the sixth.
Kansas City tied the score on DeJesus' RBI double in the third and Mike Sweeney's run-scoring single in the fifth.
Hidalgo's seventh-inning drive off Andy Sisco was his eighth homer, giving Hidalgo his 14th multihomer game.
Matt Diaz tripled with one out in the sixth for Kansas City. With the infield in, John Buck grounded to shortstop Michael Young,
who threw to the plate, where Barajas tagged out Diaz during a collision in which Diaz tried to knock the ball out of Barajas' grasp.
"It's a contact play," Diaz said. "The ball's on the ground, and you're just getting ready for a collision. ... I tried to jar the ball loose."
The teams opened their 10-game season series, with seven to be played in Kansas City. ... The Royals, who hadn't drawn a walk in their previous two games, got two among their first six batters, with Matt Stairs and Teahen drawing passes. ... Hidalgo's previous two-homer game was last July for the Mets against the Montreal Expos. ... Texas' David Dellucci, who leads the majors with 37 walks, struck out four times. ... Of Mench's last 12 hits, 10 have been for extra bases.