Summer Highlights at Lake Arrowhead Resort : Mountain village offers lodging discounts. More bargains in Monterey.

The mountain community of Lake Arrowhead, nestled some 5,500 feet up in the San Bernardino Mountains, is offering a series of senior discounts for lodging and various sightseeing and activity programs in the area. Among the highlights:

* Elderhostel educational travel programs are offered at the Lake Arrowhead Resort (until recently the Lake Arrowhead Hilton), where a six-day learning program includes three days of classes, room accommodations, all meals and use of the hotel’s extensive recreational facilities for $355 per person. Participants must be 60 years of age or older; minimum age for a companion is 50. Complete Elderhostel information is available from College of the Desert, Community Services Department, 43-500 Monterey Ave., Palm Desert 92260, (619) 773-2544.

* The Lake Arrowhead Resort offers “SuperSaver” rates that provide 50% discounts off weekday room rates, and 25% off Saturday. Weekday rates for seniors from now through Sept. 13 are $79.50 per room per night, and $119 on Saturday (the regular rate is $159 per night, weekdays and weekends). From Sept. 14 to Jan. 3, 1994, rates are further reduced to $74.50 weekdays and $109 Saturday (regular rate for this time of year: $149). For reservations and information, call (800) 800-6792.

Other discounts for seniors at Lake Arrowhead Village include:

* 10% off the price of a two-hour ecology walk of nature trails; seniors pay $18. (909) 337-5080.

* $1 off the regular $9.50 fare for a one-hour Lake Arrowhead cruise on the Arrowhead Queen paddle-wheeler. (909) 336-6992.

* $1 off the regular $5 rate for a two-hour skating session at the Ice Castle in Blue Jay, training camp home of the National Hockey League’s Los Angeles Kings. Skate rental is also reduced $1 for seniors. (909) 336-2111.

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Several hotels in the Monterey area of Northern California are offering senior discounts that will remain in effect through 1993.

* The Doubletree Hotel Monterey has a “Silver Leaf” program that provides 20% off nightly room rates year-round to members of AARP or anyone over the age of 55. Rates are reduced to $116 double occupancy and $100 single, down from $145 and $125.

A 15% discount for seniors is also offered on “early bird” dinners served from 5 to 7 p.m. Information and reservations: (800) 528-0444.

* The Monterey Hotel, Mariposa Motor Inn and Waystation Inn are offering a “Seasoned Travelers” special, Sundays through Thursdays. A two-night minimum stay is required at each hotel to qualify for the per-night room rate of $55.

The Monterey Hotel is a European-style bed and breakfast with 45 guest rooms. Regular rates range $79-$139 per night. (800) 727-0960.

The Mariposa Motor Inn is about a five-minute drive from downtown. Regular rates range $68-$98. (800) 824-2295.

The Waystation Inn sits in a wooded area near the Monterey Airport, close to both Monterey and Carmel. Regular rates range $59-$89. (800) 858-0822.