We the People 200. All roads lead to Philadelphia in 1987 - and this year's ongoing celebration of the United States Constitution's 200th anniversary. The so-called ``Miracle at Philadelphia'' can be experienced through special events taking place daily in the city. Major events will occur on Memorial Day weekend, on July 4, and on the anniversary of the signing of the Constitution, Sept. 17. For details on the celebration, write the Philadelphia Convention and Visitors Bureau, 1515 Market Street, Suite 2020, Philadelphia, PA 19109 or call toll-free, 1-800-523-2004, ext. 87.
Mary, Queen of Scots, remembered. Thirty historical sites in Scotland will spotlight places, displays, and collections associated with the life of Mary, Queen of Scots, who died 400 years ago this year. An April-September exhibition at her residence, Earlshall Castle, will display items she owned and documents of the time. Visitors can also follow ``Mary's Trail,'' which recreates routes she took during seven years of travel. Five-day vacation packages are available from Icelandair. which include a night in Reykjavik, Iceland (site of the October 1986 summit between President Reagan and Secretary Gorbachev). Package prices range from $689 to $799. For more information, see your travel agent and ask about ``The Great Scot Adventure,'' or call 800-223-5500.
Motorhome and camper rental in Europe. Connex offers a summer program in Europe for camper and motorhome rentals, with prices starting at $239 a week. Modest to luxurious vehicles are being offered for pick-up in Britain, Belgium, Germany, Italy, and Holland. All rentals are made at guaranteed dollar rates, with no additional charges for currency fluctuations. For more information, contact Connex, 983 Main St., Peekskill, NY 10566, or call 800-445-7404 (in most states), 800-642-0669 (NY), or 800-642-0669 (Canada).
Wildlife tour on Galapagos Islands. Cheesemans' Ecology Safaris offers a unique vacation for non-smokers July 28-Aug 13. Departing from San Francisco, 14 adventurers will spend eight days in Galapagos, Ecuador, and then travel to Machu Picchu, Peru, via Lima and Cuzco. Sites include Incan ruins, spectacular wildlife, and the beautiful scenery of South America. Land cost is $1,750 (including all lodging and meals), plus $1,426 for airfare from Ecuatoriana to Galapagos and Cuzco. For more information, write Cheesemans' Ecology Safaris, Inc. 20800 Kittredge Road, Saratoga, CA 95070; (408) 867-1371.
International arts in Charleston, S.C. The 11th annual Spoleto Festival USA takes place May 22-June 7 in Charleston, S.C., featuring music, dance, opera, theater, and visual arts from all over the world. Spiros Argiris comes from Greece to make his debut as the festival's new music director, conducting Richard Strauss's ``Salom'e.'' From the US comes the Merce Cuningham Dance Company, from South African playwright Athol Fugard directing and performing his drama ``The Road to Mecca.'' Italy's Colla Family Marionettes present the Old-World tradition of miniature theater, and Brazil's dancers of Jelon Vierira DanceBrazil create and compete in the dance/martial-art form of capoeira. For more information and tickets, call the Spoleto box office at (803) 577-7863. Tickets can also be purchased through Teletron 800-233-4050.
Llama trek in Vermont. The llama, South American cousin to the camel, treds lightly on padded feet, making it ecologically ideal for trail travel. Also able to carry up to 100 pounds of gear, the llama can leave hikers free to enjoy their surroundings. Country Inns Along the Trail offers overnight and day llama treks in Vermont's scenic mountains. All trips include an introduction to the animals and instruction in packing techniques. Overnight treks include tents and community dining equipment (personal gear and sleeping bags must be brought by campers). Treks may also be planned in conjunction with inn-to-inn hiking or bicycling trips. For more information, write Country Inns Along the Trail, the Churchill House Inn, R.D. No. 3, Box PR, Brandon, VT 05733, or call (802) 247-3300.
See Vietnam firsthand. Orient Flexi-pax Tours (OFPT) offers two tours - the Vietnam Mini Pax (seven days) and Vietnam in Depth (nine days) with weekly departures. The Vietnam Mini Pax focuses on the country's two major cities, Saigon, and Hanoi. Vietnam in Depth takes visitors from the mountain towns and coastal villages north of Hanoi south to the Mekong Delta flatlands. Costs range from $1,179 for the Mini Pax to $1,1779 for the in Depth program per person, double occupancy, including air and land expenses within Vietnam. Accommodations are comfortable but not luxurious. For more information, contact your travel agent or Orient Flexi-Pax Tours at 630 Third Ave., New York, NY 10017; or call 800-223-7460 (nationwide), (212) 692-9550 (New York), 800-843-843-6635 (Canada).
The Other Spain. Explore the mountains, villages, and coasts of Northern Spain on an 18-day tour beginning Sept. 25. Mountaineer Martin Zabaleta leads hikes in the Sierra de Gredos, Picos de Europa, Aragon Pyrenees, and along the Basque coast with visits to ancient towns in Aragon, Catalonia, and Euskadi. ``The Other Spain'' is $1,770. For more information, write Mountain Travel, 1398 Solano Ave., Albany, CA 94706, or call 800-227-2384 or (415) 527-8100 in California.