Update

I am in Guatemala City, staying at the offices of Sister Parish (family connections); I am learning that it is an excellent organization connecting parishes in the US with ones in Guatemala and El Salvador, creating solidarity, cross-cultural understanding, and exchange of ideas and resources.
My objectives here are to replace a few parts on my bicycle: front derailleur, tires, new rimstrip in the front. I have had fun biking around the city, visiting bike shops in search of the derailleur. Finally found a shop that has it, Pro Bikes by José, and I am currently in the process of proposing an exchange of help: I give them positive publicity and some recorded English lessons, and they give me the spare parts I need. I will report back later on that.
It is nice to be in a place with all the products and services I could ask for; I am rather confident that nowhere else in Guatemala has the replacement bike part I need, and conveniences like reliable, high-speed internet, grocery stores, cafés, etc. are abundant here.
Once I obtain the parts I need and the bike is ready to go again, I plan to head back to Antigua, then to San Andres Itzapa, home of Maya Pedal, then to San Lucas Toliman on Lago Atitlán, and then to Esquintla, San José (beach), along the beach and then into El Salvador, taking a coastal route. Such is the current plan. Hilly territory ahead, most of it paved, then then it is downhill to the coast, followed by relatively flat terrain for awhile.