These guys love using the "low channels" (frequencies below CB channel 1). The "low band" or "band C" seems to be where they hang out the most (26.515 MHz to 26.955 MHz).
26.555 MHz LSB - Latin America SSB DX calling frequency (see also: 27.455 MHz USB) - stations will QSY from 26.555 LSB onto 26.545 MHz LSB, 26.565 MHz LSB, 26.525 MHz LSB, 26.540 MHz LSB, 26.570 MHz LSB and others.
26.515 MHz AM - I've heard taxi cab companies, US stations and lots of Latin American chatter on here
26.525 MHz AM - alternate AM frequency, also used for SSB freebanders (in LSB mode)
26.535 MHz AM - alternate AM frequency, taxi cab dispatcher (in AM mode) and SSB freebanders (in LSB mode)
26.545 MHz AM - mostly used for SSB activity (in LSB mode), but I've heard AM signals on here too
26.555 MHz LSB - Yep, very busy
26.565 MHz AM - alternate frequency
26.575 MHz AM - alternate frequency
26.585 MHz AM - big radios, big power - Mexican trucker and freebander frequency
26.595 MHz AM - alternate frequency when 26.585MHz AM is just going nuts (as it often is)
26.605 MHz AM - very popular
26.615 MHz AM
26.625 MHz AM
26.635 MHz AM - very popular with Mexican freeband CB operators and others
26.645 MHz AM
26.655 MHz AM - another popular frequency
26.665 MHz AM - I've noticed Spanish language chatter on here a lot more lately
26.675 MHz AM - US stations, Spanish language also noted
26.685 MHz AM - Spanish language, also taxi cab dispatcher YLs, also US truck drivers (identified as ABF (trucking company) use?)
26.695 MHz AM - Mexican accented Spanish, also big radios out of Florida, Puerto Rico and Caribbean area
26.705 MHz AM - BIG radios out of Puerto Rico and other areas (see also: 26.695 AM, 26.715 AM, 26.725 AM)
26.715 MHz AM - BIG radios (similar to 26.705 AM)
26.725 MHz AM - alternate to 26.705 MHz AM and 26.715 MHz AM
26.735 MHz AM - Lots of truck drivers on here, but also Latin American traffic
26.745 MHz AM - taxi cab dispatch YL (Spanish language) heard here
26.755 MHz AM - Spanish language and English speaking freebanders
26.765 MHz AM - Mexican taxi cab dispatcher, female YL dispatch lady, very strong signal at points
26.775 MHz AM - I've heard a lot of stations out of the southern USA on this frequency
26.785 MHz AM
26.795 MHz AM
26.805 MHz AM - Spanish language stations, note: this is unofficially now a FM frequency 26.805FM
26.805 MHz FM - US freeband CB operators, FM mode, very popular 26.805 FM or 805 FM club
26.815 MHz AM - US stations, mostly
26.825 MHz AM
26.835 MHz AM
26.845 MHz AM
26.855 MHz AM
26.865 MHz AM
26.875 MHz AM
26.885 MHz AM - US stations, including those that QSY'ed from 26.915 AM, etc
26.895 MHz AM
26.905 MHz AM - Known taxi dispatcher frequency, also US freebanders QSYed from 26.915 AM
26.915 MHz AM - BIG radios, commonly called "36 low" or "915"
26.925 MHz AM - Lots of different users on here
26.935 MHz AM - I've heard lots of Spanish here, also taxi dispatcher lady
26.945 MHz AM - US stations, running power, and Spanish speaking taxi cab dispatch comms
26.955 MHz AM - Taxi dispatcher (Spanish), and also lots of US freebanders
The lower channels, that is, Band A (25.615 MHz - 26.055 MHz) and Band B (26.065 MHz to 26.505 MHz) so overall
25.615 MHz up to 26.505 MHz is very popular with
Freeband SSB operators, usually clustered around 26.285 MHz USB, 26.225 MHz USB and a handful of others
Taxi cab companies (all over!)
Truckers (mostly on 25.835 MHz AM but heard all over)
Hunters, hunt club channels
Forestry, farmers, etc. using a "clear channel"
From what I've read, many CB users in Latin America are either using:
Export radios (aka "10 meter" radios) which cover:
25.615 MHz to 30.105 MHz - the new "standard" - Chinese rigs
26.515 MHz to 27.855 MHz - "120 channel" CB rigs, usually with a "LOW/MID/HIGH" band switch (CB band is "MID")
25.615 MHz to 27.405 MHz - Hunting radios, with A-B-C-D band switch (CB band is "Band D")
26.065 MHz to 27.405 MHz - Hunting radios, with B-C-D band switch (CB band is "Band D"
25.615 MHz to 28.305 MHz - the 6-band "240 channel" A-B-C-D-E-F band standard plan (CB Band is "Band D")
25.165 MHz to 28.755 MHz - the 8-band "320 channel" band plan
24.265 MHz to 29.655 MHz - Superstar 158EDX and several other radios
Or, modified CB rigs that have had frequency expansion modifications done on them,
80 channel modification:
26.515 MHz to 27.405 MHz - channels 1-40 are the same as regular CB channels 1-40, channels 41-80 are the "low channels"
26.515 MHz to 27.855 MHz - very popular "120 channel" mod or "expansion" modification, gives the user three sets of 40 channels - low channels (26.515 - 26.955 MHz), mid channels/CB channels (26.965 - 27.405 MHz, the standard CB band), and high channels (27.415 - 27.855 MHz). Most of these radios also include the addition of a +10 kHz switch or a "+10kc" switch, allowing the user to access the skipped channels, LesComm, Viagra, Expo 100 and numerous other kits include kits to turn a regular 40 channel CB into a 120 channel CB.
Other kits include the addition of the "B Band" (26.065 MHz - 26.505 MHz) for a total of 120 channels, or even more coverage (for example, 25.995 MHz to 28.045 MHz, 26.005 MHz to 27.995 MHz, 26.695 MHz to 27.965 MHz, etc.