Clyde, as promised, here's our itinerary. Did it all with a rental car, total 19 WHS in 13/14 days:
26.12. evening arrival to Mexico City, night at hotel
27.12. Great Pyramid of Tenochtitlan (WHS), Cathedral, Palace, Fine Arts Museum, Post museum. Afternoon Chapultepec – Anthropological museum, palace and gardens, Museo Tamayo and Tequila and Mezcal museum in the evening at the Mariachi plaza
28.12. Teotihuacan in the morning (WHS), drive to El Tajin with a stop to Padre Telembeque Aqueduct (WHS). Sightseeing at El Tajín (WHS), drive back to Mexico City, dinner, night at the hotel.
29.12. Early morning sightseeing of the University complex (WHS), then drive to Coyoacán, visit to Leon Trotsky Casa, skipped Casa Azul as the crews were insane. Drove to Louis Barragan house and studio (WHS), guided tour, then drove to Querétaro (2xWHS). Late lunch/early dinner there, rest of the day spent sightseeing around.
30.12. Day-trip to Sierra Gorda, stop at El Chuvejé waterfall, visiting Jalpán and Landa (mission churches) (WHS), lunch at Jalpán. Visited Bernal on the way back. Night at Querétaro.
31.12. Visit to San Miguel de Allende (WHS), drive to Guanajuato (WHS). Visited the Mummy museum, walked around town, had an early dinner and spent New Year's at the panoramic terrace of hour guesthouse.
1.1. Drive to Zacatecas (WHS), visited Cerro de la Bufa, walking around town, vsiting the sights.
2.1. Morning visit to Rafael Coronel museum, drive to Guadalajara. Left the car at the hotel, visited Hospicio Cabanas (WHS), walked around the town, visited the cathedral.
3.1. Day trip to Tequila (WHS) with tour of fields and distilleries.
4.1. Drive to Morelia (WHS), afternoon spent sightseeing.
5.1. Day trip around Lake Patzcuaro: Pátzcuaro with its museum, church and market, Tocuaro with the mask makers, and Tzintzuntzan. Night at Morelia.
6.1. Early morning ride to Angangueo, to see the Monarch butterflies (WHS). Then ride to Cuernavaca to see one of the monasteries at the slopes of Popocatepetl (WHS). Ride to nearby Xochicalco (WHS), late afternoon visit. Drive to Taxco, night there.
7.1. Early morning sightseeing of Taxco, drive to Puebla (WHS). Afternoon and evening spent sightseeing Puebla.
8.1. Morning trip to Cholula and Cacaxtla, drive to the airport, evening flight home.