The start of the semifinals of the...

The start of the semifinals of the NBA Playoffs, the second jewel of thoroughbred racing’s Triple Crown, Game 3 of the NHL Stanley Cup finals and two games between the N.Y. Mets and the Dodgers highlight the weekend’s sports television viewing choices.

* Pro Basketball: The Lakers open the Western Conference Final series against the Portland Trail Blazers today at 12:30 p.m. on Channels 4, 36 and 39. The same channels will air either Game 7 of the Boston Celtics-Detroit Pistons Eastern Conference semifinal series or Game 1 of the Eastern Conference Final series Sunday at 12:30 p.m. At halftime, the NBA will conduct its draft lottery.

* Horse Racing: ABC’s (Channels 7, 3, 10 and 42) coverage of the Preakness Stakes begins at 1:30 p.m. today with post time scheduled at 2:32. ESPN has a 12:30 p.m. Preakness Stakes special.

* Pro Hockey: The NHL Stanley Cup Finals moves to Bloomington, Minn., Sunday, with SportsChannel’s coverage of Game 3 between the Minnesota North Stars and Pittsburgh Penguins beginning at 5 p.m. The game will air on a pay-per-view basis in the San Diego area.

* Baseball: CBS will televise the Mets-Dodgers game today at noon on Channel. 2. KFMB Channel 8 in San Diego will join the game in progress at 1 p.m. Sunday’s game between the teams airs on WWOR beginning at 1 p.m. but is subject to blackout in a 35-mile radius of Dodger Stadium. KTLA Channel 5 will air the Angels-Baltimore Orioles games today at 4:30 p.m. and Sunday at 10:30 a.m.

* Boxing: Greg Haugen, who upset World Boxing Organization junior-welterweight champion Hector (Macho) Camacho Feb. 23, fights Camacho again, 7 p.m. tonight on HBO. Former heavyweight champion George Foreman debuts as a commentator, joining KCBS Channel 2 anchor Jim Lampley and Larry Merchant.